<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:0bcca2f2-477b-4da4-b64a-5454cac083d7,g:4c57189b-f164-423f-ad8a-41e6af3d28e1-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://fivestarbank.com/role/CONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITYUnaudited" xlink:type="simple" xlink:href="fsbc-20250630.xsd#CONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITYUnaudited"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/CONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITYUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_65efe1d0-0283-4889-9436-75d15f950f27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5406b343-260d-4c19-9283-cd938d639f09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_65efe1d0-0283-4889-9436-75d15f950f27" xlink:to="loc_us-gaap_StatementTable_5406b343-260d-4c19-9283-cd938d639f09" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_f76b55d3-6487-4a56-b11b-60a7a0891616" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5406b343-260d-4c19-9283-cd938d639f09" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_f76b55d3-6487-4a56-b11b-60a7a0891616" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_f76b55d3-6487-4a56-b11b-60a7a0891616_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f76b55d3-6487-4a56-b11b-60a7a0891616" xlink:to="loc_us-gaap_EquityComponentDomain_f76b55d3-6487-4a56-b11b-60a7a0891616_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_606a336c-49b9-43f9-b4d5-9592418c54e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f76b55d3-6487-4a56-b11b-60a7a0891616" xlink:to="loc_us-gaap_EquityComponentDomain_606a336c-49b9-43f9-b4d5-9592418c54e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_6d3adce7-5655-4eba-ad92-329e6ce21f8b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_606a336c-49b9-43f9-b4d5-9592418c54e6" xlink:to="loc_us-gaap_CommonStockMember_6d3adce7-5655-4eba-ad92-329e6ce21f8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_baa94e15-42fd-4bf8-93d3-670edba7c1c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_606a336c-49b9-43f9-b4d5-9592418c54e6" xlink:to="loc_us-gaap_RetainedEarningsMember_baa94e15-42fd-4bf8-93d3-670edba7c1c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9e844761-6bdd-434a-b814-0b5c6502abc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_606a336c-49b9-43f9-b4d5-9592418c54e6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9e844761-6bdd-434a-b814-0b5c6502abc1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_65efe1d0-0283-4889-9436-75d15f950f27" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_4d5559c7-2118-45d1-83b4-eda2f914f45c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_4d5559c7-2118-45d1-83b4-eda2f914f45c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4e647867-dc69-42b3-b1d7-110ae04f985a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockholdersEquity_4e647867-dc69-42b3-b1d7-110ae04f985a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_027130b2-055a-43a3-8ec9-4711ac88131a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_NetIncomeLoss_027130b2-055a-43a3-8ec9-4711ac88131a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_fd70af52-0964-42aa-9373-aa19c1e9b357" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_fd70af52-0964-42aa-9373-aa19c1e9b357" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_ec224e7e-46ca-46f8-806c-1546252c5206" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_ec224e7e-46ca-46f8-806c-1546252c5206" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_5b3174ab-c5ca-48f8-bdbe-762c165c8360" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_5b3174ab-c5ca-48f8-bdbe-762c165c8360" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_da589a10-fafa-4584-85e1-26b5d5bc56bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_da589a10-fafa-4584-85e1-26b5d5bc56bc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation_d4942540-b66c-4fad-a698-b5d2fea1dc79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation_d4942540-b66c-4fad-a698-b5d2fea1dc79" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_22da2133-f893-48a5-8bcd-e08a6b0dde10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_22da2133-f893-48a5-8bcd-e08a6b0dde10" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_97354b2d-a120-4a9a-96e8-53deb964e84d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_a23b3155-d4ca-4cb3-b60c-cdee30766b52" xlink:to="loc_us-gaap_DividendsCommonStock_97354b2d-a120-4a9a-96e8-53deb964e84d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_5597dd33-5e3e-4203-b64c-aeec39c02006" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4e189740-2997-4286-8f87-25828837c204" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/FairValueofAssetsandLiabilitiesFairValueofAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#FairValueofAssetsandLiabilitiesFairValueofAssetsandLiabilitiesMeasuredonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/FairValueofAssetsandLiabilitiesFairValueofAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_51a577a8-974b-4c8b-bb9c-510ac17e79fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_ecf30e0d-d826-4b42-95c8-59ca30d7db20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_51a577a8-974b-4c8b-bb9c-510ac17e79fa" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_ecf30e0d-d826-4b42-95c8-59ca30d7db20" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a53dfc3c-4891-47d4-a117-7927d0350f6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_ecf30e0d-d826-4b42-95c8-59ca30d7db20" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a53dfc3c-4891-47d4-a117-7927d0350f6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_a53dfc3c-4891-47d4-a117-7927d0350f6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a53dfc3c-4891-47d4-a117-7927d0350f6e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_a53dfc3c-4891-47d4-a117-7927d0350f6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_ff40fd3d-003a-4a2d-8c67-662ed9328fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a53dfc3c-4891-47d4-a117-7927d0350f6e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_ff40fd3d-003a-4a2d-8c67-662ed9328fe7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_d7490238-471d-4db9-9fba-601065b0aa35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_ff40fd3d-003a-4a2d-8c67-662ed9328fe7" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_d7490238-471d-4db9-9fba-601065b0aa35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c7afa099-e47b-4842-8ad2-78b73bab1ed1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_ecf30e0d-d826-4b42-95c8-59ca30d7db20" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c7afa099-e47b-4842-8ad2-78b73bab1ed1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c7afa099-e47b-4842-8ad2-78b73bab1ed1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c7afa099-e47b-4842-8ad2-78b73bab1ed1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c7afa099-e47b-4842-8ad2-78b73bab1ed1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_eb55657f-9a41-4d62-9913-bc04bf6a9ab0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c7afa099-e47b-4842-8ad2-78b73bab1ed1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_eb55657f-9a41-4d62-9913-bc04bf6a9ab0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsTotalMember_080e6f43-347c-4260-bc92-0b0abaa33470" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_eb55657f-9a41-4d62-9913-bc04bf6a9ab0" xlink:to="loc_us-gaap_AssetsTotalMember_080e6f43-347c-4260-bc92-0b0abaa33470" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_35be50aa-a6f1-4689-b294-96636698bbd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_ecf30e0d-d826-4b42-95c8-59ca30d7db20" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_35be50aa-a6f1-4689-b294-96636698bbd1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_35be50aa-a6f1-4689-b294-96636698bbd1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_35be50aa-a6f1-4689-b294-96636698bbd1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_35be50aa-a6f1-4689-b294-96636698bbd1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_93001372-3dc7-4c0d-94da-b2a80f53498a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_35be50aa-a6f1-4689-b294-96636698bbd1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_93001372-3dc7-4c0d-94da-b2a80f53498a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_4cc589ca-9ef2-4d43-8540-9f60a6e7b73d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_93001372-3dc7-4c0d-94da-b2a80f53498a" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_4cc589ca-9ef2-4d43-8540-9f60a6e7b73d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_b588433b-d0d4-4f08-98e6-da8ea3b7e85d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_93001372-3dc7-4c0d-94da-b2a80f53498a" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_b588433b-d0d4-4f08-98e6-da8ea3b7e85d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_5fde4190-da3f-4df3-9f3d-52c838b8abf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_93001372-3dc7-4c0d-94da-b2a80f53498a" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_5fde4190-da3f-4df3-9f3d-52c838b8abf1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8911d091-1f35-4b2c-a117-46db8218be55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_51a577a8-974b-4c8b-bb9c-510ac17e79fa" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8911d091-1f35-4b2c-a117-46db8218be55" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/FairValueofAssetsandLiabilitiesFairValueEstimatesforFinancialInstrumentsbyBalanceSheetGroupingDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#FairValueofAssetsandLiabilitiesFairValueEstimatesforFinancialInstrumentsbyBalanceSheetGroupingDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/FairValueofAssetsandLiabilitiesFairValueEstimatesforFinancialInstrumentsbyBalanceSheetGroupingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_6c2f121c-c3a4-4507-baca-d7346dd35f99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_17b388b9-6554-4c7c-893f-47e0f5d5edf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_6c2f121c-c3a4-4507-baca-d7346dd35f99" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_17b388b9-6554-4c7c-893f-47e0f5d5edf1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_0e3a3026-c287-4680-81ba-617d199b62d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_17b388b9-6554-4c7c-893f-47e0f5d5edf1" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_0e3a3026-c287-4680-81ba-617d199b62d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_0e3a3026-c287-4680-81ba-617d199b62d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_0e3a3026-c287-4680-81ba-617d199b62d9" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_0e3a3026-c287-4680-81ba-617d199b62d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cffdbae1-9a6f-4a32-a1c0-e48a18abfe46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_0e3a3026-c287-4680-81ba-617d199b62d9" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cffdbae1-9a6f-4a32-a1c0-e48a18abfe46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_96caf11c-63a2-4203-9eb4-b9ed63bbd559" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cffdbae1-9a6f-4a32-a1c0-e48a18abfe46" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_96caf11c-63a2-4203-9eb4-b9ed63bbd559" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_dddc5c1c-060f-48ba-9dc0-b589d7be8d3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_96caf11c-63a2-4203-9eb4-b9ed63bbd559" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_dddc5c1c-060f-48ba-9dc0-b589d7be8d3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_d534203c-b04f-4562-bcb0-46bfb8cd6378" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_96caf11c-63a2-4203-9eb4-b9ed63bbd559" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_d534203c-b04f-4562-bcb0-46bfb8cd6378" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_17b388b9-6554-4c7c-893f-47e0f5d5edf1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7524f8a3-9b5e-4c67-986f-ef0f74c23c05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9cc34af6-28d2-4e2d-9a4b-68ca5124dc13" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7524f8a3-9b5e-4c67-986f-ef0f74c23c05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_a649525f-4cc9-47d1-952d-af55671b4870" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7524f8a3-9b5e-4c67-986f-ef0f74c23c05" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_a649525f-4cc9-47d1-952d-af55671b4870" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_f88b4d58-6d5d-4ac9-ad56-b2365de49d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7524f8a3-9b5e-4c67-986f-ef0f74c23c05" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_f88b4d58-6d5d-4ac9-ad56-b2365de49d5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_34805c50-e690-4c15-8dcd-fd25bc68ae91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7524f8a3-9b5e-4c67-986f-ef0f74c23c05" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_34805c50-e690-4c15-8dcd-fd25bc68ae91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:href="fsbc-20250630.xsd#fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_6c2f121c-c3a4-4507-baca-d7346dd35f99" xlink:to="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_1f361dad-672d-4e51-9863-fda861abb3bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_1f361dad-672d-4e51-9863-fda861abb3bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_TimeDepositAtFairValueDisclosure_f7204ea3-4fdd-425a-bb1a-9aaceae35472" xlink:href="fsbc-20250630.xsd#fsbc_TimeDepositAtFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_fsbc_TimeDepositAtFairValueDisclosure_f7204ea3-4fdd-425a-bb1a-9aaceae35472" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_a7a8e433-e1ae-4247-b517-96c8cec3d419" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_a7a8e433-e1ae-4247-b517-96c8cec3d419" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_4653be38-4b57-4dd1-bf9b-69b29dae8308" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_4653be38-4b57-4dd1-bf9b-69b29dae8308" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_eabe6a74-fc80-45d6-91da-0b798ba41741" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_eabe6a74-fc80-45d6-91da-0b798ba41741" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_e2df081f-ee2a-40c9-819a-3e867c8352ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialAssetsRecordedAtAmortizedCostAbstract_edbbae9c-434d-491b-a6ab-6685c56ffabb" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_e2df081f-ee2a-40c9-819a-3e867c8352ef" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FinancialLiabilitiesRecordedAtAmortizedCostAbstract_e6d45804-707f-45e0-9c9d-60e49f60bacf" xlink:href="fsbc-20250630.xsd#fsbc_FinancialLiabilitiesRecordedAtAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_6c2f121c-c3a4-4507-baca-d7346dd35f99" xlink:to="loc_fsbc_FinancialLiabilitiesRecordedAtAmortizedCostAbstract_e6d45804-707f-45e0-9c9d-60e49f60bacf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_TimeDepositsFairValueDisclosure_a8317efb-2ff5-4c3f-9722-e10328837ac5" xlink:href="fsbc-20250630.xsd#fsbc_TimeDepositsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialLiabilitiesRecordedAtAmortizedCostAbstract_e6d45804-707f-45e0-9c9d-60e49f60bacf" xlink:to="loc_fsbc_TimeDepositsFairValueDisclosure_a8317efb-2ff5-4c3f-9722-e10328837ac5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations_4fc684b9-61e6-489f-be29-4785a48d25b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FinancialLiabilitiesRecordedAtAmortizedCostAbstract_e6d45804-707f-45e0-9c9d-60e49f60bacf" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations_4fc684b9-61e6-489f-be29-4785a48d25b7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesHeldtoMaturityDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesHeldtoMaturityDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesHeldtoMaturityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_7232d7ea-4dec-4f93-a779-b1d36f1a3660" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_MarketableSecuritiesTable_7232d7ea-4dec-4f93-a779-b1d36f1a3660" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_fb68355f-93e5-40e5-90f5-18b3638c5464" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_7232d7ea-4dec-4f93-a779-b1d36f1a3660" xlink:to="loc_us-gaap_FinancialInstrumentAxis_fb68355f-93e5-40e5-90f5-18b3638c5464" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb68355f-93e5-40e5-90f5-18b3638c5464_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fb68355f-93e5-40e5-90f5-18b3638c5464" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fb68355f-93e5-40e5-90f5-18b3638c5464_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_154b8b96-ad6b-4424-a96e-7f6e193fc842" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fb68355f-93e5-40e5-90f5-18b3638c5464" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_154b8b96-ad6b-4424-a96e-7f6e193fc842" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_2ad6162c-6824-44cf-97a0-c9c275923983" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_154b8b96-ad6b-4424-a96e-7f6e193fc842" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_2ad6162c-6824-44cf-97a0-c9c275923983" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss_1e5cc6ea-820c-4f67-b23b-dac8c71017b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss_1e5cc6ea-820c-4f67-b23b-dac8c71017b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_11ef7092-0918-46fd-ba86-3d298583d3b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_HeldToMaturitySecurities_11ef7092-0918-46fd-ba86-3d298583d3b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_68321267-0d24-4029-bdf8-4ad5fe527bb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_68321267-0d24-4029-bdf8-4ad5fe527bb1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_3b67d1b4-159d-4a1a-bfdb-1ac63db86288" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_3b67d1b4-159d-4a1a-bfdb-1ac63db86288" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_473a2da8-17ed-4b8d-a444-d9da827ef7a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_ff2c8174-bc98-4019-80a1-14a291c2b1b6" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_473a2da8-17ed-4b8d-a444-d9da827ef7a3" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesAvailableforSaleDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesAvailableforSaleDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofSecuritiesAvailableforSaleDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_e732f264-9359-4edc-833c-27755f6a6884" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:to="loc_us-gaap_MarketableSecuritiesTable_e732f264-9359-4edc-833c-27755f6a6884" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_be031874-68ff-4d58-9c0f-9167681eb0b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_e732f264-9359-4edc-833c-27755f6a6884" xlink:to="loc_us-gaap_FinancialInstrumentAxis_be031874-68ff-4d58-9c0f-9167681eb0b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_be031874-68ff-4d58-9c0f-9167681eb0b3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_be031874-68ff-4d58-9c0f-9167681eb0b3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_be031874-68ff-4d58-9c0f-9167681eb0b3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_be031874-68ff-4d58-9c0f-9167681eb0b3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_4916c345-f2c3-4442-862d-ae40b7ad85be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_4916c345-f2c3-4442-862d-ae40b7ad85be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_bcd69374-cc39-47ea-adc7-0e1271d46557" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_bcd69374-cc39-47ea-adc7-0e1271d46557" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_0aa9f9f6-528a-4bff-9883-1c9b33d32be4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_0aa9f9f6-528a-4bff-9883-1c9b33d32be4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedDebtObligationsMember_74481660-a274-4f18-a147-3a17c5053e02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralizedDebtObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:to="loc_us-gaap_CollateralizedDebtObligationsMember_74481660-a274-4f18-a147-3a17c5053e02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_df5e75da-b2e4-4ad6-9e1a-1f0a6a709fab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_debed1f6-8432-4a62-bea6-2db09ad9d3c3" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_df5e75da-b2e4-4ad6-9e1a-1f0a6a709fab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_06b89895-0c14-4e1a-a174-bbc22fa6fcc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_06b89895-0c14-4e1a-a174-bbc22fa6fcc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_2d19f00d-fb7d-49a9-9f44-733d2a482e9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_2d19f00d-fb7d-49a9-9f44-733d2a482e9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_42a2bdb3-ab10-4712-b7e4-d10b2edca72c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_42a2bdb3-ab10-4712-b7e4-d10b2edca72c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e0e53484-9d26-438f-9345-a0720c842a69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1be8135a-95ad-490e-8a5e-fbecbbe2af90" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e0e53484-9d26-438f-9345-a0720c842a69" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofInvestmentDebtSecuritiesbyContractualMaturityDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InvestmentSecuritiesAmortizedCostandFairValueofInvestmentDebtSecuritiesbyContractualMaturityDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InvestmentSecuritiesAmortizedCostandFairValueofInvestmentDebtSecuritiesbyContractualMaturityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_84df8416-8616-480c-8a85-4be4677a712c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_MarketableSecuritiesTable_84df8416-8616-480c-8a85-4be4677a712c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_375f40e0-8a85-4db1-a540-c111eb27f62c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_84df8416-8616-480c-8a85-4be4677a712c" xlink:to="loc_us-gaap_FinancialInstrumentAxis_375f40e0-8a85-4db1-a540-c111eb27f62c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_375f40e0-8a85-4db1-a540-c111eb27f62c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_375f40e0-8a85-4db1-a540-c111eb27f62c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_375f40e0-8a85-4db1-a540-c111eb27f62c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_375f40e0-8a85-4db1-a540-c111eb27f62c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_2cfde4ba-a310-4c3a-98b8-a9f01aa30c40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_2cfde4ba-a310-4c3a-98b8-a9f01aa30c40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_a2d06208-8d73-410c-9ae6-103e544f5487" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_a2d06208-8d73-410c-9ae6-103e544f5487" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedDebtObligationsMember_9cc0b47e-f21f-42d7-8ded-b681a0b762c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralizedDebtObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:to="loc_us-gaap_CollateralizedDebtObligationsMember_9cc0b47e-f21f-42d7-8ded-b681a0b762c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_48e3c1fe-1eed-4371-b7bc-5357aa51a9c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_99f6aa16-56b5-4537-88b7-efef325cc6a6" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_48e3c1fe-1eed-4371-b7bc-5357aa51a9c9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract_fe0ea1a2-96ef-4054-9138-230401a6685d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract_fe0ea1a2-96ef-4054-9138-230401a6685d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract_fe0ea1a2-96ef-4054-9138-230401a6685d" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_fa582872-094c-489e-8f69-e18a191de9ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_fa582872-094c-489e-8f69-e18a191de9ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount_6984e6d0-26cd-4fd2-a457-0fa9ee5f6f5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount_6984e6d0-26cd-4fd2-a457-0fa9ee5f6f5d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount_8f2eed6e-a67d-4ad0-808c-3ca1772e9aa7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount_8f2eed6e-a67d-4ad0-808c-3ca1772e9aa7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount_1aaa0186-4962-43c2-9bd6-3f24a22354cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_fb3f7788-657a-4af5-8206-8e546be1debc" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount_1aaa0186-4962-43c2-9bd6-3f24a22354cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAbstract_fe0ea1a2-96ef-4054-9138-230401a6685d" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue_db72bc6a-5e7a-480d-a748-f427e9c025ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue_db72bc6a-5e7a-480d-a748-f427e9c025ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_8978d5f4-4d1d-40a9-b536-325ae3c02927" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_8978d5f4-4d1d-40a9-b536-325ae3c02927" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_21d84371-f5a9-4523-a8f4-bd57df4f7a24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_21d84371-f5a9-4523-a8f4-bd57df4f7a24" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue_a7e1c8b7-7414-44fe-9218-b51b607cea3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValueAbstract_7d6d8688-2148-41a4-af3d-747ded1f2da2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue_a7e1c8b7-7414-44fe-9218-b51b607cea3d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_7011b0c8-316d-43f1-896e-e13d74d86d92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_7011b0c8-316d-43f1-896e-e13d74d86d92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_7011b0c8-316d-43f1-896e-e13d74d86d92" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_6b513d1c-2ea8-4ee9-85d9-bfc15879bb20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_6b513d1c-2ea8-4ee9-85d9-bfc15879bb20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_236b43a5-8868-4c4c-a63c-873048123882" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_236b43a5-8868-4c4c-a63c-873048123882" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_8fdd7eb7-5d4f-4748-a22f-102bec562d2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_8fdd7eb7-5d4f-4748-a22f-102bec562d2f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_230d1e9b-5d21-44f9-b04d-075c960dc548" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_98891254-33fd-41d7-8826-f7f558873982" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_230d1e9b-5d21-44f9-b04d-075c960dc548" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_7011b0c8-316d-43f1-896e-e13d74d86d92" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_8769de2c-caba-4188-a6e2-759e97f76095" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_8769de2c-caba-4188-a6e2-759e97f76095" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_0937e412-f122-42fa-bcca-f5e81dac487c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_0937e412-f122-42fa-bcca-f5e81dac487c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_603f1923-2e67-415f-8f8e-1673f93c548e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_603f1923-2e67-415f-8f8e-1673f93c548e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_c1265998-8bc7-4a7d-86b7-5176a19b8ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_dead3d74-5f56-48dd-8a74-b76f2f308de6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_c1265998-8bc7-4a7d-86b7-5176a19b8ebc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_47a7e5dd-40c1-4529-848e-d458acc24206" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_HeldToMaturitySecurities_47a7e5dd-40c1-4529-848e-d458acc24206" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_8e9e2591-3752-4c08-893b-a9e6c95aeae4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_8e9e2591-3752-4c08-893b-a9e6c95aeae4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_153b7d2c-4fd6-4833-b49c-d396a478926b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_153b7d2c-4fd6-4833-b49c-d396a478926b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_7041f44e-0c8c-4b3a-a8c0-bf7b948f3c76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_1fcd8db3-7b0b-4e15-b3e9-97bb34593610" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_7041f44e-0c8c-4b3a-a8c0-bf7b948f3c76" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InvestmentSecuritiesPledgedInvestmentSecuritiesDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InvestmentSecuritiesPledgedInvestmentSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InvestmentSecuritiesPledgedInvestmentSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_dfe6896c-bf22-4928-8815-feb66947669f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_972d82c6-8bc5-43be-93e5-039f3afdc03c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_dfe6896c-bf22-4928-8815-feb66947669f" xlink:to="loc_us-gaap_MarketableSecuritiesTable_972d82c6-8bc5-43be-93e5-039f3afdc03c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_2b6c1c13-7879-4d8b-a455-d1240cfef1f8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_972d82c6-8bc5-43be-93e5-039f3afdc03c" xlink:to="loc_srt_StatementGeographicalAxis_2b6c1c13-7879-4d8b-a455-d1240cfef1f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_2b6c1c13-7879-4d8b-a455-d1240cfef1f8_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_2b6c1c13-7879-4d8b-a455-d1240cfef1f8" xlink:to="loc_srt_SegmentGeographicalDomain_2b6c1c13-7879-4d8b-a455-d1240cfef1f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_83ebf967-2acd-4682-a211-588033e4132a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_2b6c1c13-7879-4d8b-a455-d1240cfef1f8" xlink:to="loc_srt_SegmentGeographicalDomain_83ebf967-2acd-4682-a211-588033e4132a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_CA_d1054712-86c3-4f67-8163-89f2d46d6c28" xlink:href="https://xbrl.sec.gov/stpr/2025/stpr-2025.xsd#stpr_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_83ebf967-2acd-4682-a211-588033e4132a" xlink:to="loc_stpr_CA_d1054712-86c3-4f67-8163-89f2d46d6c28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeAxis_a472013e-c320-44b0-89b2-a2b243236209" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_972d82c6-8bc5-43be-93e5-039f3afdc03c" xlink:to="loc_us-gaap_PledgingPurposeAxis_a472013e-c320-44b0-89b2-a2b243236209" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_a472013e-c320-44b0-89b2-a2b243236209_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgingPurposeAxis_a472013e-c320-44b0-89b2-a2b243236209" xlink:to="loc_us-gaap_PledgingPurposeDomain_a472013e-c320-44b0-89b2-a2b243236209_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_0ce70d76-8f0a-4dd9-9562-8aa947216dec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgingPurposeAxis_a472013e-c320-44b0-89b2-a2b243236209" xlink:to="loc_us-gaap_PledgingPurposeDomain_0ce70d76-8f0a-4dd9-9562-8aa947216dec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsMember_d2f76dcb-15ed-4cfa-b584-e04eb89081af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_0ce70d76-8f0a-4dd9-9562-8aa947216dec" xlink:to="loc_us-gaap_DepositsMember_d2f76dcb-15ed-4cfa-b584-e04eb89081af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedMember_0ac1a384-7825-4c27-bcab-70deeec3ceb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalFundsPurchasedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_0ce70d76-8f0a-4dd9-9562-8aa947216dec" xlink:to="loc_us-gaap_FederalFundsPurchasedMember_0ac1a384-7825-4c27-bcab-70deeec3ceb3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_DepositsAndFederalFundsPurchasedMember_d05ef631-b85a-4b71-a7e7-6c51fe202545" xlink:href="fsbc-20250630.xsd#fsbc_DepositsAndFederalFundsPurchasedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_0ce70d76-8f0a-4dd9-9562-8aa947216dec" xlink:to="loc_fsbc_DepositsAndFederalFundsPurchasedMember_d05ef631-b85a-4b71-a7e7-6c51fe202545" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_65587c4b-5e35-406b-8fcb-91a1f7406f8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_dfe6896c-bf22-4928-8815-feb66947669f" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_65587c4b-5e35-406b-8fcb-91a1f7406f8f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InvestmentSecuritiesAvailableforSaleSecuritiesinaContinuousUnrealizedLossPositionDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InvestmentSecuritiesAvailableforSaleSecuritiesinaContinuousUnrealizedLossPositionDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InvestmentSecuritiesAvailableforSaleSecuritiesinaContinuousUnrealizedLossPositionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_1d9150c7-41f0-4dfb-8b4d-7b7b5c4ff99f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_us-gaap_MarketableSecuritiesTable_1d9150c7-41f0-4dfb-8b4d-7b7b5c4ff99f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_1d9150c7-41f0-4dfb-8b4d-7b7b5c4ff99f" xlink:to="loc_us-gaap_FinancialInstrumentAxis_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_aeb785bb-d57a-4c9b-81b2-6e7c608a0b02" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_bea6a3ef-3035-4909-a87d-51ab041badc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_bea6a3ef-3035-4909-a87d-51ab041badc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_2f5016a3-7849-42a3-a056-79cfe43d8693" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_2f5016a3-7849-42a3-a056-79cfe43d8693" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_b8013a30-5d80-4a60-a465-59ba92caab1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_b8013a30-5d80-4a60-a465-59ba92caab1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedDebtObligationsMember_4b363a95-22b7-4750-9890-0fa3a6673767" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralizedDebtObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:to="loc_us-gaap_CollateralizedDebtObligationsMember_4b363a95-22b7-4750-9890-0fa3a6673767" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_0bc1624a-b5b8-4070-ae60-d8e633c47616" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6f92685a-35b6-4458-8b33-15cc6af001cf" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_0bc1624a-b5b8-4070-ae60-d8e633c47616" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_1c443655-555e-44a8-b0a9-98b08ef7b8d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_1c443655-555e-44a8-b0a9-98b08ef7b8d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_8f07d911-d8de-417e-9dfc-f1193bdc7f3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_8f07d911-d8de-417e-9dfc-f1193bdc7f3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerFairValue_867466c5-511c-4232-a651-9a33d46f7f1c" xlink:href="fsbc-20250630.xsd#fsbc_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_fsbc_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerFairValue_867466c5-511c-4232-a651-9a33d46f7f1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_c7bcfd4a-a581-46b7-b185-96f1488135da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_c7bcfd4a-a581-46b7-b185-96f1488135da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValue_7ca47e1e-e074-437d-873b-71e64826f56c" xlink:href="fsbc-20250630.xsd#fsbc_DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_fsbc_DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValue_7ca47e1e-e074-437d-873b-71e64826f56c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_4227d7be-08a2-4f10-bec6-1205d4a245f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_38e845a9-31c3-4354-9f12-86c84addfc7b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_4227d7be-08a2-4f10-bec6-1205d4a245f8" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesBalanceofEachMajorProductTypeDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesBalanceofEachMajorProductTypeDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesBalanceofEachMajorProductTypeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_a9dac83a-c0f3-4d2a-be52-dd60063a17f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_a9dac83a-c0f3-4d2a-be52-dd60063a17f1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ecfa1d91-c1aa-44c7-a1a3-11105180ba76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_a9dac83a-c0f3-4d2a-be52-dd60063a17f1" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ecfa1d91-c1aa-44c7-a1a3-11105180ba76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ecfa1d91-c1aa-44c7-a1a3-11105180ba76_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ecfa1d91-c1aa-44c7-a1a3-11105180ba76" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ecfa1d91-c1aa-44c7-a1a3-11105180ba76_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ecfa1d91-c1aa-44c7-a1a3-11105180ba76" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_7d5e61b5-fde9-4949-a2ad-1876824ec42a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_us-gaap_CommercialRealEstateMember_7d5e61b5-fde9-4949-a2ad-1876824ec42a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_d6858869-d917-4184-8871-0fe68eac441f" xlink:href="fsbc-20250630.xsd#fsbc_RealEstateCommercialLandAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_d6858869-d917-4184-8871-0fe68eac441f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CommercialConstructionLoansMember_23de83d7-c49b-46e3-9fff-37bd7f010fa3" xlink:href="fsbc-20250630.xsd#fsbc_CommercialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_fsbc_CommercialConstructionLoansMember_23de83d7-c49b-46e3-9fff-37bd7f010fa3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ResidentialConstructionLoansMember_39b77b18-8b8a-421c-b061-5f0e76570e50" xlink:href="fsbc-20250630.xsd#fsbc_ResidentialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_fsbc_ResidentialConstructionLoansMember_39b77b18-8b8a-421c-b061-5f0e76570e50" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_08b681ff-b719-4e16-a106-433895fe50f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_us-gaap_ResidentialRealEstateMember_08b681ff-b719-4e16-a106-433895fe50f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FarmlandMember_d40f801b-9a81-497c-8241-0c5dfb28997e" xlink:href="fsbc-20250630.xsd#fsbc_FarmlandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_fsbc_FarmlandMember_d40f801b-9a81-497c-8241-0c5dfb28997e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_3136d2f1-fb1d-42d2-b1a8-bd754ff2cf45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_us-gaap_SecuredDebtMember_3136d2f1-fb1d-42d2-b1a8-bd754ff2cf45" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_ee59329c-8432-4d14-9778-a79f945febca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_us-gaap_UnsecuredDebtMember_ee59329c-8432-4d14-9778-a79f945febca" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_d8d0d6c3-f5bc-4f7b-bb13-502db6944c53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ee152e2c-bbe2-43d6-b3a0-254c7f29aab7" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_d8d0d6c3-f5bc-4f7b-bb13-502db6944c53" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee_20daa6bf-3f9c-4bde-8deb-301327eb8b96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee_20daa6bf-3f9c-4bde-8deb-301327eb8b96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_3275d0d8-7ba5-4cbd-b6dc-2a50430d7d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_3275d0d8-7ba5-4cbd-b6dc-2a50430d7d5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_87a9014b-9df6-40df-b672-a629b2de47b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_NotesReceivableGross_87a9014b-9df6-40df-b672-a629b2de47b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_066dd764-6790-4165-8b64-f23da7342f15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_066dd764-6790-4165-8b64-f23da7342f15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_c44457e5-796e-45a5-8c56-9e21db7af795" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_a4091243-40c6-4481-8cfa-da595cd94642" xlink:to="loc_us-gaap_NotesReceivableNet_c44457e5-796e-45a5-8c56-9e21db7af795" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesCreditQualityIndicatorsRelatedtotheCompanysLoansbyClassDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesCreditQualityIndicatorsRelatedtotheCompanysLoansbyClassDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesCreditQualityIndicatorsRelatedtotheCompanysLoansbyClassDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_15f6898b-6bdf-48ad-82d0-75930bf3d0a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_15f6898b-6bdf-48ad-82d0-75930bf3d0a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_dff63e7f-937a-4db7-9b28-1aa85021605f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_15f6898b-6bdf-48ad-82d0-75930bf3d0a2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_dff63e7f-937a-4db7-9b28-1aa85021605f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_dff63e7f-937a-4db7-9b28-1aa85021605f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_dff63e7f-937a-4db7-9b28-1aa85021605f" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_dff63e7f-937a-4db7-9b28-1aa85021605f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_dff63e7f-937a-4db7-9b28-1aa85021605f" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_3bf4f34a-830f-420d-8f22-deb28015f7c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_us-gaap_CommercialRealEstateMember_3bf4f34a-830f-420d-8f22-deb28015f7c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_29b29abd-ddf8-4bb1-8ecd-5ec9d1a448c0" xlink:href="fsbc-20250630.xsd#fsbc_RealEstateCommercialLandAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_29b29abd-ddf8-4bb1-8ecd-5ec9d1a448c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CommercialConstructionLoansMember_c4e19877-5ca6-4a6c-a69d-4757235d339f" xlink:href="fsbc-20250630.xsd#fsbc_CommercialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_fsbc_CommercialConstructionLoansMember_c4e19877-5ca6-4a6c-a69d-4757235d339f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ResidentialConstructionLoansMember_bd6e7fa7-2541-4cdb-8eaf-ac77c38694ee" xlink:href="fsbc-20250630.xsd#fsbc_ResidentialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_fsbc_ResidentialConstructionLoansMember_bd6e7fa7-2541-4cdb-8eaf-ac77c38694ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_8045c133-72c1-4ad0-bed0-0c9b68365542" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_us-gaap_ResidentialRealEstateMember_8045c133-72c1-4ad0-bed0-0c9b68365542" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FarmlandMember_58d55995-4084-47e1-b66b-8b1707cbb8b6" xlink:href="fsbc-20250630.xsd#fsbc_FarmlandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_fsbc_FarmlandMember_58d55995-4084-47e1-b66b-8b1707cbb8b6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_7bb3df8a-9335-4572-96c4-22e1b8980805" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_us-gaap_SecuredDebtMember_7bb3df8a-9335-4572-96c4-22e1b8980805" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_710ccb24-273b-4799-b42a-9c742433f817" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_us-gaap_UnsecuredDebtMember_710ccb24-273b-4799-b42a-9c742433f817" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_d72ed495-a541-459b-b4dc-ee95aa0d9b6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_93083821-b82e-4adc-afed-96dfe51617c7" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_d72ed495-a541-459b-b4dc-ee95aa0d9b6f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_3a58e208-5461-4455-899d-9e5af65ed592" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_15f6898b-6bdf-48ad-82d0-75930bf3d0a2" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_3a58e208-5461-4455-899d-9e5af65ed592" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_3a58e208-5461-4455-899d-9e5af65ed592_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_3a58e208-5461-4455-899d-9e5af65ed592" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_3a58e208-5461-4455-899d-9e5af65ed592_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_75bf5de0-892b-43a3-8075-8caf0d192094" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_3a58e208-5461-4455-899d-9e5af65ed592" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_75bf5de0-892b-43a3-8075-8caf0d192094" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassMember_ed0ae0bc-fe95-4225-96ab-c8baa1eab1a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_75bf5de0-892b-43a3-8075-8caf0d192094" xlink:to="loc_us-gaap_PassMember_ed0ae0bc-fe95-4225-96ab-c8baa1eab1a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_WatchMember_4708b1f9-257a-4465-85bd-cfea4ac2d135" xlink:href="fsbc-20250630.xsd#fsbc_WatchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_75bf5de0-892b-43a3-8075-8caf0d192094" xlink:to="loc_fsbc_WatchMember_4708b1f9-257a-4465-85bd-cfea4ac2d135" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubstandardMember_e46e12b8-581b-498f-b4fd-37e1a54eeb20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubstandardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_75bf5de0-892b-43a3-8075-8caf0d192094" xlink:to="loc_us-gaap_SubstandardMember_e46e12b8-581b-498f-b4fd-37e1a54eeb20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear_9d811269-a280-40d2-b58e-648b70790450" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear_9d811269-a280-40d2-b58e-648b70790450" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear_fdd4930f-14c9-4831-a33f-ee0a99f4a5f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear_fdd4930f-14c9-4831-a33f-ee0a99f4a5f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear_4edb1ad5-c086-4d7b-84c0-b121f68fff79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear_4edb1ad5-c086-4d7b-84c0-b121f68fff79" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear_057281cf-d797-49fa-869b-efe7844e3d16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear_057281cf-d797-49fa-869b-efe7844e3d16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear_4e1cad54-0ee7-4919-ad20-ba0c935d95a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear_4e1cad54-0ee7-4919-ad20-ba0c935d95a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear_f2c12dcf-bde7-420b-bef0-19be6fa5b81f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear_f2c12dcf-bde7-420b-bef0-19be6fa5b81f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRevolving_51f2cc5a-b121-45c6-a57c-41b1fe4887d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableRevolving_51f2cc5a-b121-45c6-a57c-41b1fe4887d2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRevolvingConvertedToTermLoan_66ed9ea4-2a90-4b1f-96e6-5b6e72459768" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRevolvingConvertedToTermLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_FinancingReceivableRevolvingConvertedToTermLoan_66ed9ea4-2a90-4b1f-96e6-5b6e72459768" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_33a3f3db-a7d3-4def-9f8a-409f55fdc1ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_cd6564cb-0b75-496d-ab85-b9add4d485c9" xlink:to="loc_us-gaap_NotesReceivableGross_33a3f3db-a7d3-4def-9f8a-409f55fdc1ef" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesAgeAnalysisofPastDueLoansbyClassDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesAgeAnalysisofPastDueLoansbyClassDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesAgeAnalysisofPastDueLoansbyClassDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_84bc265f-7d28-408d-b348-ef1595b1bbe6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2af143b1-2d27-4d87-8a3b-0b483cb7e880" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_84bc265f-7d28-408d-b348-ef1595b1bbe6" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2af143b1-2d27-4d87-8a3b-0b483cb7e880" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_819024d7-0eeb-47d6-9b2d-79132441860a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2af143b1-2d27-4d87-8a3b-0b483cb7e880" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_819024d7-0eeb-47d6-9b2d-79132441860a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_819024d7-0eeb-47d6-9b2d-79132441860a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_819024d7-0eeb-47d6-9b2d-79132441860a" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_819024d7-0eeb-47d6-9b2d-79132441860a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_819024d7-0eeb-47d6-9b2d-79132441860a" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_4009e0aa-203d-442a-ad73-6584302f4c60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_us-gaap_CommercialRealEstateMember_4009e0aa-203d-442a-ad73-6584302f4c60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_644711df-1238-49d5-a318-e53cdd576722" xlink:href="fsbc-20250630.xsd#fsbc_RealEstateCommercialLandAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_644711df-1238-49d5-a318-e53cdd576722" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CommercialConstructionLoansMember_000208ba-e683-4805-b96d-86a8e5b6b0c6" xlink:href="fsbc-20250630.xsd#fsbc_CommercialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_fsbc_CommercialConstructionLoansMember_000208ba-e683-4805-b96d-86a8e5b6b0c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ResidentialConstructionLoansMember_82242680-ab5f-42eb-a258-40f470f35b27" xlink:href="fsbc-20250630.xsd#fsbc_ResidentialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_fsbc_ResidentialConstructionLoansMember_82242680-ab5f-42eb-a258-40f470f35b27" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_6b623893-151e-471d-82da-5186aa588c92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_us-gaap_ResidentialRealEstateMember_6b623893-151e-471d-82da-5186aa588c92" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FarmlandMember_aa8df888-3e8c-43c3-b004-c0799b49651e" xlink:href="fsbc-20250630.xsd#fsbc_FarmlandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_fsbc_FarmlandMember_aa8df888-3e8c-43c3-b004-c0799b49651e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_1c1abeef-bbad-4e91-bd4f-a4ef6e61d537" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_us-gaap_SecuredDebtMember_1c1abeef-bbad-4e91-bd4f-a4ef6e61d537" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_cb14871a-e859-4a53-b081-cd626a04b17b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_us-gaap_UnsecuredDebtMember_cb14871a-e859-4a53-b081-cd626a04b17b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_3abc0b64-8572-44e9-bcf0-c2cd1e75cda6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a07b6d2-6a8e-4e0e-b5ea-e2a688534a8e" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_3abc0b64-8572-44e9-bcf0-c2cd1e75cda6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_f1c8ae83-269a-4d53-bdc9-6184a827d4dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2af143b1-2d27-4d87-8a3b-0b483cb7e880" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_f1c8ae83-269a-4d53-bdc9-6184a827d4dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_f1c8ae83-269a-4d53-bdc9-6184a827d4dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_f1c8ae83-269a-4d53-bdc9-6184a827d4dc" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_f1c8ae83-269a-4d53-bdc9-6184a827d4dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_f1c8ae83-269a-4d53-bdc9-6184a827d4dc" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_1837157b-e3f9-43d8-8723-08139f5c9531" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_1837157b-e3f9-43d8-8723-08139f5c9531" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_9fc563cd-f30b-44a9-b464-8ce7931161e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_9fc563cd-f30b-44a9-b464-8ce7931161e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_3d15de06-1509-4caa-b5e3-45a82a12a7e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_3d15de06-1509-4caa-b5e3-45a82a12a7e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetPastDueMember_3fc724b2-f4b5-421b-9e3f-faf66baae922" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:to="loc_us-gaap_FinancialAssetPastDueMember_3fc724b2-f4b5-421b-9e3f-faf66baae922" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_8fb102d6-a350-440d-842b-d842202da92b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_cc71cc9f-ff38-4ef7-868d-5d80dd0f556a" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_8fb102d6-a350-440d-842b-d842202da92b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_1f6ce5cf-f65b-46f5-8bba-cf033cb7b0ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_84bc265f-7d28-408d-b348-ef1595b1bbe6" xlink:to="loc_us-gaap_NotesReceivableGross_1f6ce5cf-f65b-46f5-8bba-cf033cb7b0ef" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesNarrativeDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_e99cefa5-495d-4fe0-a462-1f612c15900b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_e99cefa5-495d-4fe0-a462-1f612c15900b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveBankBranchAxis_5f1733a1-bcdf-46b5-8053-93b916aba999" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveBankBranchAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_e99cefa5-495d-4fe0-a462-1f612c15900b" xlink:to="loc_fsbc_FederalReserveBankBranchAxis_5f1733a1-bcdf-46b5-8053-93b916aba999" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveBankBranchDomain_5f1733a1-bcdf-46b5-8053-93b916aba999_default" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveBankBranchDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_fsbc_FederalReserveBankBranchAxis_5f1733a1-bcdf-46b5-8053-93b916aba999" xlink:to="loc_fsbc_FederalReserveBankBranchDomain_5f1733a1-bcdf-46b5-8053-93b916aba999_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveBankBranchDomain_f771a136-47e2-484b-bf24-7aa54e3e1b5f" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveBankBranchDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_fsbc_FederalReserveBankBranchAxis_5f1733a1-bcdf-46b5-8053-93b916aba999" xlink:to="loc_fsbc_FederalReserveBankBranchDomain_f771a136-47e2-484b-bf24-7aa54e3e1b5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveBankOfSanFranciscoMember_564d57bc-3140-4b7c-aa7c-43dff65e5106" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveBankOfSanFranciscoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_FederalReserveBankBranchDomain_f771a136-47e2-484b-bf24-7aa54e3e1b5f" xlink:to="loc_fsbc_FederalReserveBankOfSanFranciscoMember_564d57bc-3140-4b7c-aa7c-43dff65e5106" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_937a88cc-264e-4913-8881-19dd86e5d19d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_e99cefa5-495d-4fe0-a462-1f612c15900b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_937a88cc-264e-4913-8881-19dd86e5d19d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_937a88cc-264e-4913-8881-19dd86e5d19d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_937a88cc-264e-4913-8881-19dd86e5d19d" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_937a88cc-264e-4913-8881-19dd86e5d19d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c12aeebb-3182-4c40-ba4c-162afb554edb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_937a88cc-264e-4913-8881-19dd86e5d19d" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c12aeebb-3182-4c40-ba4c-162afb554edb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_e2210507-c4e0-4fc1-af50-406b19d319c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c12aeebb-3182-4c40-ba4c-162afb554edb" xlink:to="loc_us-gaap_CommercialRealEstateMember_e2210507-c4e0-4fc1-af50-406b19d319c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing_0ec9bc35-2626-4ded-96a3-26b672dcd4e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing_0ec9bc35-2626-4ded-96a3-26b672dcd4e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_NumberOfCollateralDependentLoansInProcessOfForeclosure_91c54535-cc54-47bf-96f6-fcaf9719875a" xlink:href="fsbc-20250630.xsd#fsbc_NumberOfCollateralDependentLoansInProcessOfForeclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_fsbc_NumberOfCollateralDependentLoansInProcessOfForeclosure_91c54535-cc54-47bf-96f6-fcaf9719875a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModificationsRecordedInvestment_dfbc01d2-83c2-442c-94f1-562b9072a216" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModificationsRecordedInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_us-gaap_FinancingReceivableModificationsRecordedInvestment_dfbc01d2-83c2-442c-94f1-562b9072a216" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_NumberOfCollateralDependentLoans_5739cba0-3232-4429-b218-b537b1d723d7" xlink:href="fsbc-20250630.xsd#fsbc_NumberOfCollateralDependentLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_fsbc_NumberOfCollateralDependentLoans_5739cba0-3232-4429-b218-b537b1d723d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FinancingReceivableCollateralDependentOutstanding_8ff19baf-8407-4ca1-96f7-df7c7acd3a1b" xlink:href="fsbc-20250630.xsd#fsbc_FinancingReceivableCollateralDependentOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_fsbc_FinancingReceivableCollateralDependentOutstanding_8ff19baf-8407-4ca1-96f7-df7c7acd3a1b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableNonaccrualInterestIncome_38e184a7-6b51-4755-ba47-4d1dfac9fc67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableNonaccrualInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_us-gaap_FinancingReceivableNonaccrualInterestIncome_38e184a7-6b51-4755-ba47-4d1dfac9fc67" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FinancingReceivableNonaccrualInterestIncomeForegone_5178a0e8-02d9-4efa-9a76-f14a8f5039de" xlink:href="fsbc-20250630.xsd#fsbc_FinancingReceivableNonaccrualInterestIncomeForegone"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_fsbc_FinancingReceivableNonaccrualInterestIncomeForegone_5178a0e8-02d9-4efa-9a76-f14a8f5039de" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1_28e0adfe-ce20-4744-bff5-2b50e99a4cca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1_28e0adfe-ce20-4744-bff5-2b50e99a4cca" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged_2b1fb377-8857-42ce-8821-a5bec483c927" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_f13879c5-ce00-4389-bd06-92f0fd7be217" xlink:to="loc_fsbc_FederalReserveBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged_2b1fb377-8857-42ce-8821-a5bec483c927" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesNonaccrualLoansSegregatedbyClassDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesNonaccrualLoansSegregatedbyClassDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesNonaccrualLoansSegregatedbyClassDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_b9f5ad92-4279-43c3-b167-7f4c6a0c7c12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2f1c853b-1ead-4e3c-a6c0-f08242aca8ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_b9f5ad92-4279-43c3-b167-7f4c6a0c7c12" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2f1c853b-1ead-4e3c-a6c0-f08242aca8ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_73885447-0f8c-48f5-b019-93df9c79f4fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_2f1c853b-1ead-4e3c-a6c0-f08242aca8ce" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_73885447-0f8c-48f5-b019-93df9c79f4fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_73885447-0f8c-48f5-b019-93df9c79f4fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_73885447-0f8c-48f5-b019-93df9c79f4fe" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_73885447-0f8c-48f5-b019-93df9c79f4fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_e65418ca-8519-4f4e-ace0-292d658cdccc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_73885447-0f8c-48f5-b019-93df9c79f4fe" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_e65418ca-8519-4f4e-ace0-292d658cdccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_336d00f2-f11a-4ce5-baa8-bcfb1764444d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_e65418ca-8519-4f4e-ace0-292d658cdccc" xlink:to="loc_us-gaap_CommercialRealEstateMember_336d00f2-f11a-4ce5-baa8-bcfb1764444d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_09516cc1-866c-403b-bbaa-b5cef0fcf692" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_e65418ca-8519-4f4e-ace0-292d658cdccc" xlink:to="loc_us-gaap_SecuredDebtMember_09516cc1-866c-403b-bbaa-b5cef0fcf692" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_56b3a970-c536-465e-a59a-0f956395d0d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_b9f5ad92-4279-43c3-b167-7f4c6a0c7c12" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_56b3a970-c536-465e-a59a-0f956395d0d6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesAllowanceforCreditLossesDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesAllowanceforCreditLossesDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesAllowanceforCreditLossesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_07348038-f33e-4800-ae02-464235d3a18a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_742e1697-948b-452d-bf1e-3f1af6b0b62f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_07348038-f33e-4800-ae02-464235d3a18a" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_742e1697-948b-452d-bf1e-3f1af6b0b62f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4ded4306-c157-4736-8166-0eeb9afa22b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_742e1697-948b-452d-bf1e-3f1af6b0b62f" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4ded4306-c157-4736-8166-0eeb9afa22b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4ded4306-c157-4736-8166-0eeb9afa22b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4ded4306-c157-4736-8166-0eeb9afa22b7" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4ded4306-c157-4736-8166-0eeb9afa22b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4ded4306-c157-4736-8166-0eeb9afa22b7" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_d6c94f76-891d-4bd2-be39-770b58cef9da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_us-gaap_CommercialRealEstateMember_d6c94f76-891d-4bd2-be39-770b58cef9da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_1d002484-b278-4222-a926-940a5280cf3f" xlink:href="fsbc-20250630.xsd#fsbc_RealEstateCommercialLandAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_fsbc_RealEstateCommercialLandAndDevelopmentMember_1d002484-b278-4222-a926-940a5280cf3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CommercialConstructionLoansMember_5a524222-38d4-468b-b1cc-a3043f7dbf16" xlink:href="fsbc-20250630.xsd#fsbc_CommercialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_fsbc_CommercialConstructionLoansMember_5a524222-38d4-468b-b1cc-a3043f7dbf16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ResidentialConstructionLoansMember_efd87703-2823-4ba9-b79a-0aac0a78ddab" xlink:href="fsbc-20250630.xsd#fsbc_ResidentialConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_fsbc_ResidentialConstructionLoansMember_efd87703-2823-4ba9-b79a-0aac0a78ddab" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_e09f3a84-9ccd-425d-9841-8186977450ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_us-gaap_ResidentialRealEstateMember_e09f3a84-9ccd-425d-9841-8186977450ce" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FarmlandMember_860b2728-98a4-4eb3-a078-e20eed6614e3" xlink:href="fsbc-20250630.xsd#fsbc_FarmlandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_fsbc_FarmlandMember_860b2728-98a4-4eb3-a078-e20eed6614e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_37118962-148a-40ab-9584-0fbad23b0acc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_us-gaap_SecuredDebtMember_37118962-148a-40ab-9584-0fbad23b0acc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_c7d5140d-c593-4579-99b5-5478e692ff65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_us-gaap_UnsecuredDebtMember_c7d5140d-c593-4579-99b5-5478e692ff65" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_ec40c4bd-d4c4-4311-be9b-eaebfdfe00b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7bf210e6-c68d-47a4-97a0-71745362dde9" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_ec40c4bd-d4c4-4311-be9b-eaebfdfe00b6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_07348038-f33e-4800-ae02-464235d3a18a" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_b0f79bec-583d-49b6-aae0-9af13e0c4664" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_b0f79bec-583d-49b6-aae0-9af13e0c4664" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs_b8aaed87-1b33-4cda-85a5-3d045c1af785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs_b8aaed87-1b33-4cda-85a5-3d045c1af785" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery_5eb01160-cd03-4cfe-92c3-83923d4f7ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery_5eb01160-cd03-4cfe-92c3-83923d4f7ef0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLossesExpensed_d85d3dc6-dbf8-4333-9c4d-86013808d050" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProvisionForLoanLossesExpensed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_b69261b6-113f-4db4-be63-7a80a59e5abf" xlink:to="loc_us-gaap_ProvisionForLoanLossesExpensed_d85d3dc6-dbf8-4333-9c4d-86013808d050" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_4deec4e4-530e-43c5-b5ea-22125cac33d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesUnfundedLoanCommitmentReserveDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#LoansandAllowanceforCreditLossesUnfundedLoanCommitmentReserveDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/LoansandAllowanceforCreditLossesUnfundedLoanCommitmentReserveDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_6974c5fc-2027-4ab8-afe3-99eb8f3871d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_16958ba6-be2b-4cb5-808d-2f99daa76e40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_6974c5fc-2027-4ab8-afe3-99eb8f3871d5" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_16958ba6-be2b-4cb5-808d-2f99daa76e40" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8a3c64e7-8880-4634-b476-072e9df20c15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_16958ba6-be2b-4cb5-808d-2f99daa76e40" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8a3c64e7-8880-4634-b476-072e9df20c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a3c64e7-8880-4634-b476-072e9df20c15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8a3c64e7-8880-4634-b476-072e9df20c15" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8a3c64e7-8880-4634-b476-072e9df20c15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_a030c603-3a42-4ad1-9f27-c5e32e8d6e6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8a3c64e7-8880-4634-b476-072e9df20c15" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_a030c603-3a42-4ad1-9f27-c5e32e8d6e6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnfundedLoanCommitmentMember_008fd756-0d70-4dd6-ae77-3d1623db9d22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnfundedLoanCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_a030c603-3a42-4ad1-9f27-c5e32e8d6e6e" xlink:to="loc_us-gaap_UnfundedLoanCommitmentMember_008fd756-0d70-4dd6-ae77-3d1623db9d22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_f71c0905-c7e3-4400-91a0-9bc3945250f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_6974c5fc-2027-4ab8-afe3-99eb8f3871d5" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_f71c0905-c7e3-4400-91a0-9bc3945250f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_b065daa9-6a3e-4808-b410-cd4ff8d711a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_f71c0905-c7e3-4400-91a0-9bc3945250f7" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_b065daa9-6a3e-4808-b410-cd4ff8d711a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLossesExpensed_8785c4d5-23af-4eb7-ad76-6d57b878e6ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProvisionForLoanLossesExpensed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_f71c0905-c7e3-4400-91a0-9bc3945250f7" xlink:to="loc_us-gaap_ProvisionForLoanLossesExpensed_8785c4d5-23af-4eb7-ad76-6d57b878e6ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_5fd007f4-61ef-4cc9-8ea1-6795bea58c2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/InterestBearingDepositsCompositionofNetworkDepositsDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#InterestBearingDepositsCompositionofNetworkDepositsDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/InterestBearingDepositsCompositionofNetworkDepositsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_InterestBearingDepositsLineItems_e2a640e5-a1f0-4589-bedd-5c03b221ff05" xlink:href="fsbc-20250630.xsd#fsbc_InterestBearingDepositsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_InterestBearingDepositsTable_900c7792-1962-44f3-8bde-c6c0c5d415fd" xlink:href="fsbc-20250630.xsd#fsbc_InterestBearingDepositsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_fsbc_InterestBearingDepositsLineItems_e2a640e5-a1f0-4589-bedd-5c03b221ff05" xlink:to="loc_fsbc_InterestBearingDepositsTable_900c7792-1962-44f3-8bde-c6c0c5d415fd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_0a232295-ca9d-4730-914a-e93fb50959e2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_fsbc_InterestBearingDepositsTable_900c7792-1962-44f3-8bde-c6c0c5d415fd" xlink:to="loc_srt_ProductOrServiceAxis_0a232295-ca9d-4730-914a-e93fb50959e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_0a232295-ca9d-4730-914a-e93fb50959e2_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_0a232295-ca9d-4730-914a-e93fb50959e2" xlink:to="loc_srt_ProductsAndServicesDomain_0a232295-ca9d-4730-914a-e93fb50959e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_740db40b-24eb-49c6-b46a-34f0ea5e6ee6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_0a232295-ca9d-4730-914a-e93fb50959e2" xlink:to="loc_srt_ProductsAndServicesDomain_740db40b-24eb-49c6-b46a-34f0ea5e6ee6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CDARSMember_bd5c4ddb-538b-46f3-a9f2-f032dbacd11c" xlink:href="fsbc-20250630.xsd#fsbc_CDARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_740db40b-24eb-49c6-b46a-34f0ea5e6ee6" xlink:to="loc_fsbc_CDARSMember_bd5c4ddb-538b-46f3-a9f2-f032dbacd11c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ICSMember_71e99a37-c4b9-4ece-a4f6-299a56c8b08e" xlink:href="fsbc-20250630.xsd#fsbc_ICSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_740db40b-24eb-49c6-b46a-34f0ea5e6ee6" xlink:to="loc_fsbc_ICSMember_71e99a37-c4b9-4ece-a4f6-299a56c8b08e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_NetworkDeposits_acd81a8c-7e3e-4ac5-9357-9326bb42a71f" xlink:href="fsbc-20250630.xsd#fsbc_NetworkDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_fsbc_InterestBearingDepositsLineItems_e2a640e5-a1f0-4589-bedd-5c03b221ff05" xlink:to="loc_fsbc_NetworkDeposits_acd81a8c-7e3e-4ac5-9357-9326bb42a71f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/SubordinatedNotesandOtherBorrowingsNarrativeDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#SubordinatedNotesandOtherBorrowingsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/SubordinatedNotesandOtherBorrowingsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_17aabe9e-4e3b-48d4-b04e-b9b78f19d6c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_DebtInstrumentTable_17aabe9e-4e3b-48d4-b04e-b9b78f19d6c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a7e5acfb-3210-4597-b009-925c40f7c84b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_17aabe9e-4e3b-48d4-b04e-b9b78f19d6c6" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a7e5acfb-3210-4597-b009-925c40f7c84b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a7e5acfb-3210-4597-b009-925c40f7c84b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a7e5acfb-3210-4597-b009-925c40f7c84b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a7e5acfb-3210-4597-b009-925c40f7c84b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a82d4fdc-f635-46bf-9e04-d9d89b5812b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a7e5acfb-3210-4597-b009-925c40f7c84b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a82d4fdc-f635-46bf-9e04-d9d89b5812b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebtMember_3a787e7e-b1de-49b2-b0eb-078a73b228ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a82d4fdc-f635-46bf-9e04-d9d89b5812b0" xlink:to="loc_us-gaap_SubordinatedDebtMember_3a787e7e-b1de-49b2-b0eb-078a73b228ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_d843a725-db5c-4a72-93e3-0a9c488dbb4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a82d4fdc-f635-46bf-9e04-d9d89b5812b0" xlink:to="loc_us-gaap_LineOfCreditMember_d843a725-db5c-4a72-93e3-0a9c488dbb4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_17aabe9e-4e3b-48d4-b04e-b9b78f19d6c6" xlink:to="loc_us-gaap_DebtInstrumentAxis_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_dc52ccc3-e67e-46e5-a2fa-37b0ce9693ed" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FixedToFloatingRateSubordinatedNotesIssuedAugust2022Member_c1ff4f80-cc51-47e6-95f1-6bcb8062ccdc" xlink:href="fsbc-20250630.xsd#fsbc_FixedToFloatingRateSubordinatedNotesIssuedAugust2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:to="loc_fsbc_FixedToFloatingRateSubordinatedNotesIssuedAugust2022Member_c1ff4f80-cc51-47e6-95f1-6bcb8062ccdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_EntityControlledByExistingAndFormerBoardMembersAndAffiliatesMember_bafdea34-5855-421d-8b7f-1f249feca53f" xlink:href="fsbc-20250630.xsd#fsbc_EntityControlledByExistingAndFormerBoardMembersAndAffiliatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:to="loc_fsbc_EntityControlledByExistingAndFormerBoardMembersAndAffiliatesMember_bafdea34-5855-421d-8b7f-1f249feca53f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FederalReserveDiscountWindowMember_b78300df-a92c-4cda-874c-39a1bfbc692e" xlink:href="fsbc-20250630.xsd#fsbc_FederalReserveDiscountWindowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:to="loc_fsbc_FederalReserveDiscountWindowMember_b78300df-a92c-4cda-874c-39a1bfbc692e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FiveUnsecuredFederalFundsLineOfCreditMember_4bf57f8c-6e0d-4b59-9574-d77439720bbb" xlink:href="fsbc-20250630.xsd#fsbc_FiveUnsecuredFederalFundsLineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d619e703-3d35-4050-b7d9-c9fa3dca5387" xlink:to="loc_fsbc_FiveUnsecuredFederalFundsLineOfCreditMember_4bf57f8c-6e0d-4b59-9574-d77439720bbb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_17aabe9e-4e3b-48d4-b04e-b9b78f19d6c6" xlink:to="loc_srt_RangeAxis_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26" xlink:to="loc_srt_RangeMember_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_229c3b2f-39c5-44dc-9082-254ba95feba6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d126c11f-bdce-49a4-b7ea-d7ccaaacfc26" xlink:to="loc_srt_RangeMember_229c3b2f-39c5-44dc-9082-254ba95feba6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_50ee3aff-42fc-43f5-b035-21d7e8e318ef" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_229c3b2f-39c5-44dc-9082-254ba95feba6" xlink:to="loc_srt_MinimumMember_50ee3aff-42fc-43f5-b035-21d7e8e318ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_b78923f0-55bc-480a-b00a-e05d444d4396" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_229c3b2f-39c5-44dc-9082-254ba95feba6" xlink:to="loc_srt_MaximumMember_b78923f0-55bc-480a-b00a-e05d444d4396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebt_b4c50e3c-0c3c-4a5c-955c-702807b34418" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_SubordinatedDebt_b4c50e3c-0c3c-4a5c-955c-702807b34418" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_eb6f8385-d30c-4f01-bd2f-25f1086e75e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_eb6f8385-d30c-4f01-bd2f-25f1086e75e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedBorrowingInterestRate_6efa9df0-580c-44f6-8e29-5beb4a6dbfaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedBorrowingInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_SubordinatedBorrowingInterestRate_6efa9df0-580c-44f6-8e29-5beb4a6dbfaf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_e09a3150-7049-427a-923f-947c54075017" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_e09a3150-7049-427a-923f-947c54075017" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_DebtInstrumentFloatingInterestRate_77b2e67c-179b-4989-a421-86d47a3b4646" xlink:href="fsbc-20250630.xsd#fsbc_DebtInstrumentFloatingInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_fsbc_DebtInstrumentFloatingInterestRate_77b2e67c-179b-4989-a421-86d47a3b4646" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_cc4eb031-9725-458f-8e86-d43ab68c068a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_cc4eb031-9725-458f-8e86-d43ab68c068a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_46e146a4-1c6b-469f-aaae-f83f0e87ff80" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedAmortizationDeferredFinanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_46e146a4-1c6b-469f-aaae-f83f0e87ff80" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_484186f8-e062-4c45-ac28-a70b036d8c75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_484186f8-e062-4c45-ac28-a70b036d8c75" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6bcd1b9e-47ac-416e-821e-54cea8c1a4e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6bcd1b9e-47ac-416e-821e-54cea8c1a4e3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_c1d1c6c0-ff4d-450b-a741-3ac7cda7edf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_c1d1c6c0-ff4d-450b-a741-3ac7cda7edf4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_NumberOfUnsecuredFederalFunds_1f5ae6ba-513b-48ba-bd95-010d541c5518" xlink:href="fsbc-20250630.xsd#fsbc_NumberOfUnsecuredFederalFunds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_fsbc_NumberOfUnsecuredFederalFunds_1f5ae6ba-513b-48ba-bd95-010d541c5518" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_NumberOfCorrespondentBanks_ffe21227-cf33-4618-8f5c-bc33c58e9733" xlink:href="fsbc-20250630.xsd#fsbc_NumberOfCorrespondentBanks"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_fsbc_NumberOfCorrespondentBanks_ffe21227-cf33-4618-8f5c-bc33c58e9733" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_dec11b48-f6fa-4873-beb6-7df3d31c3d88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c630c80b-3ac4-40c2-a892-07949684c198" xlink:to="loc_us-gaap_LineOfCredit_dec11b48-f6fa-4873-beb6-7df3d31c3d88" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/SubordinatedNotesandOtherBorrowingsScheduleofBorrowingCapacityDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#SubordinatedNotesandOtherBorrowingsScheduleofBorrowingCapacityDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/SubordinatedNotesandOtherBorrowingsScheduleofBorrowingCapacityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_b48c6d8e-e1df-49c6-a03b-fd78e00bcf9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:to="loc_us-gaap_DebtInstrumentTable_b48c6d8e-e1df-49c6-a03b-fd78e00bcf9b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_539c9826-a65d-4bcc-8210-f0d61dd7fb8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b48c6d8e-e1df-49c6-a03b-fd78e00bcf9b" xlink:to="loc_us-gaap_DebtInstrumentAxis_539c9826-a65d-4bcc-8210-f0d61dd7fb8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_539c9826-a65d-4bcc-8210-f0d61dd7fb8c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_539c9826-a65d-4bcc-8210-f0d61dd7fb8c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_539c9826-a65d-4bcc-8210-f0d61dd7fb8c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_71b39ed8-1261-43c0-a37b-3c50010e2650" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_539c9826-a65d-4bcc-8210-f0d61dd7fb8c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_71b39ed8-1261-43c0-a37b-3c50010e2650" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_FHLBAgreementMember_0cebeaae-a4df-4a55-be2e-1fa08e9fa903" xlink:href="fsbc-20250630.xsd#fsbc_FHLBAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_71b39ed8-1261-43c0-a37b-3c50010e2650" xlink:to="loc_fsbc_FHLBAgreementMember_0cebeaae-a4df-4a55-be2e-1fa08e9fa903" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_LettersOfCreditPledgedAsSecurityForStateOfCaliforniaDepositsMember_c9825650-f6c1-49f0-8bc0-02456578d7f2" xlink:href="fsbc-20250630.xsd#fsbc_LettersOfCreditPledgedAsSecurityForStateOfCaliforniaDepositsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_71b39ed8-1261-43c0-a37b-3c50010e2650" xlink:to="loc_fsbc_LettersOfCreditPledgedAsSecurityForStateOfCaliforniaDepositsMember_c9825650-f6c1-49f0-8bc0-02456578d7f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_SecureLocalAgencyDepositMember_85a2a419-95f0-45b8-b52e-f8cc952cfd7b" xlink:href="fsbc-20250630.xsd#fsbc_SecureLocalAgencyDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_71b39ed8-1261-43c0-a37b-3c50010e2650" xlink:to="loc_fsbc_SecureLocalAgencyDepositMember_85a2a419-95f0-45b8-b52e-f8cc952cfd7b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0565b760-4499-42e0-836d-8346c2e66380" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b48c6d8e-e1df-49c6-a03b-fd78e00bcf9b" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0565b760-4499-42e0-836d-8346c2e66380" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0565b760-4499-42e0-836d-8346c2e66380_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0565b760-4499-42e0-836d-8346c2e66380" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0565b760-4499-42e0-836d-8346c2e66380_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_1b540e95-b23f-41a2-a607-a91e0789dab6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0565b760-4499-42e0-836d-8346c2e66380" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_1b540e95-b23f-41a2-a607-a91e0789dab6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_7b8d50dc-b57c-4589-9039-719512431ff8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_1b540e95-b23f-41a2-a607-a91e0789dab6" xlink:to="loc_us-gaap_LineOfCreditMember_7b8d50dc-b57c-4589-9039-719512431ff8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_6cadc53f-1fa6-41f0-adf5-6a3eb64ea1ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_1b540e95-b23f-41a2-a607-a91e0789dab6" xlink:to="loc_us-gaap_LetterOfCreditMember_6cadc53f-1fa6-41f0-adf5-6a3eb64ea1ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_74824f68-4859-4ffe-b3c7-c5a0b61a0265" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_74824f68-4859-4ffe-b3c7-c5a0b61a0265" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_757d0c94-71c7-483a-8815-5ab2166a67aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:to="loc_us-gaap_LineOfCredit_757d0c94-71c7-483a-8815-5ab2166a67aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_9d379614-9dac-485d-9d72-d93cadf25c93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_9d379614-9dac-485d-9d72-d93cadf25c93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_30ae8e0c-8c4d-4c35-9666-824d2cc1cb1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8d0f90c7-b521-431f-8d1e-22e350ccb73d" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_30ae8e0c-8c4d-4c35-9666-824d2cc1cb1b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/ShareholdersEquityNarrativeDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#ShareholdersEquityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/ShareholdersEquityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:to="loc_us-gaap_GranteeStatusAxis_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b" xlink:to="loc_us-gaap_GranteeStatusDomain_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_ab8ca8b5-a887-4c7a-b749-7e32ae0b508b" xlink:to="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ShareBasedPaymentArrangementExecutivesAndDirectorsMember_df62240b-da96-47b2-a18a-a0bac257f5c5" xlink:href="fsbc-20250630.xsd#fsbc_ShareBasedPaymentArrangementExecutivesAndDirectorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:to="loc_fsbc_ShareBasedPaymentArrangementExecutivesAndDirectorsMember_df62240b-da96-47b2-a18a-a0bac257f5c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_0fc0a95e-a40f-4aef-a71b-298d7f03930d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedPaymentArrangementEmployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_0fc0a95e-a40f-4aef-a71b-298d7f03930d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ShareBasedPaymentArrangementExecutivesMember_45075fbc-2007-4076-9068-23b277e6f283" xlink:href="fsbc-20250630.xsd#fsbc_ShareBasedPaymentArrangementExecutivesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:to="loc_fsbc_ShareBasedPaymentArrangementExecutivesMember_45075fbc-2007-4076-9068-23b277e6f283" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ShareBasedPaymentArrangementDirectorsMember_d572699d-0a88-4990-a052-ea2cdc7e06f2" xlink:href="fsbc-20250630.xsd#fsbc_ShareBasedPaymentArrangementDirectorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_079fa798-fb85-4b13-bf43-28dc2f7809cf" xlink:to="loc_fsbc_ShareBasedPaymentArrangementDirectorsMember_d572699d-0a88-4990-a052-ea2cdc7e06f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_ed857538-d241-48d0-aee1-cdae52d5be69" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:to="loc_srt_RangeAxis_ed857538-d241-48d0-aee1-cdae52d5be69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ed857538-d241-48d0-aee1-cdae52d5be69_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_ed857538-d241-48d0-aee1-cdae52d5be69" xlink:to="loc_srt_RangeMember_ed857538-d241-48d0-aee1-cdae52d5be69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9b3a4a81-1970-444c-a087-23849f24b8f8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_ed857538-d241-48d0-aee1-cdae52d5be69" xlink:to="loc_srt_RangeMember_9b3a4a81-1970-444c-a087-23849f24b8f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5be08ef3-ea11-47c1-ba7a-e2844f5c7312" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9b3a4a81-1970-444c-a087-23849f24b8f8" xlink:to="loc_srt_MinimumMember_5be08ef3-ea11-47c1-ba7a-e2844f5c7312" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_bacb8a3d-774c-4d6a-ae92-cdfc5eb5418a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9b3a4a81-1970-444c-a087-23849f24b8f8" xlink:to="loc_srt_MaximumMember_bacb8a3d-774c-4d6a-ae92-cdfc5eb5418a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_fc591957-cdc8-497b-a9db-baeacf5760e9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:to="loc_srt_TitleOfIndividualAxis_fc591957-cdc8-497b-a9db-baeacf5760e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_fc591957-cdc8-497b-a9db-baeacf5760e9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_fc591957-cdc8-497b-a9db-baeacf5760e9" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_fc591957-cdc8-497b-a9db-baeacf5760e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_3262f292-93ba-4ce8-acd0-4247df0fa519" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_fc591957-cdc8-497b-a9db-baeacf5760e9" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_3262f292-93ba-4ce8-acd0-4247df0fa519" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OfficerMember_f7d5d2bd-f070-4069-bb59-3286245be3b0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_OfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_3262f292-93ba-4ce8-acd0-4247df0fa519" xlink:to="loc_srt_OfficerMember_f7d5d2bd-f070-4069-bb59-3286245be3b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveOfficerMember_ca2a074b-3213-4325-845e-756300825c7b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_3262f292-93ba-4ce8-acd0-4247df0fa519" xlink:to="loc_srt_ExecutiveOfficerMember_ca2a074b-3213-4325-845e-756300825c7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_8a7562b7-b496-487d-88a8-d268b2426a91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:to="loc_us-gaap_PlanNameAxis_8a7562b7-b496-487d-88a8-d268b2426a91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8a7562b7-b496-487d-88a8-d268b2426a91_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_8a7562b7-b496-487d-88a8-d268b2426a91" xlink:to="loc_us-gaap_PlanNameDomain_8a7562b7-b496-487d-88a8-d268b2426a91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_08726aec-c23d-4f7c-8ab9-2dfdb26aec05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_8a7562b7-b496-487d-88a8-d268b2426a91" xlink:to="loc_us-gaap_PlanNameDomain_08726aec-c23d-4f7c-8ab9-2dfdb26aec05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_EquityIncentivePlanMember_b5e5c222-51e0-4adc-8e29-1db97d667da2" xlink:href="fsbc-20250630.xsd#fsbc_EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_08726aec-c23d-4f7c-8ab9-2dfdb26aec05" xlink:to="loc_fsbc_EquityIncentivePlanMember_b5e5c222-51e0-4adc-8e29-1db97d667da2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_60965242-de90-4970-86f1-08e2a4e3f1a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb4d2dbe-1c2e-41bd-8906-d05c77bb1d74" xlink:to="loc_us-gaap_AwardTypeAxis_60965242-de90-4970-86f1-08e2a4e3f1a3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_60965242-de90-4970-86f1-08e2a4e3f1a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_60965242-de90-4970-86f1-08e2a4e3f1a3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_60965242-de90-4970-86f1-08e2a4e3f1a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a779fb55-ab44-4a3a-9642-667d75bc8772" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_60965242-de90-4970-86f1-08e2a4e3f1a3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a779fb55-ab44-4a3a-9642-667d75bc8772" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_8cd98fab-5fbe-4694-b3dd-6d08a66728a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a779fb55-ab44-4a3a-9642-667d75bc8772" xlink:to="loc_us-gaap_RestrictedStockMember_8cd98fab-5fbe-4694-b3dd-6d08a66728a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_1d390160-7e81-4904-8748-ec245c3b69c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_1d390160-7e81-4904-8748-ec245c3b69c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_dbd54db6-338e-4876-94da-1679f6846f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_DividendsCommonStock_dbd54db6-338e-4876-94da-1679f6846f7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_5d01acbf-0a96-4465-9151-95786bac42d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_5d01acbf-0a96-4465-9151-95786bac42d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_c3b98470-6e41-42c2-a0a6-b03ffb0f2eac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_ShareBasedCompensation_c3b98470-6e41-42c2-a0a6-b03ffb0f2eac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_03be9cd9-3931-4a8e-aeb4-116165fd0986" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_03be9cd9-3931-4a8e-aeb4-116165fd0986" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_UnvestedRestrictedShares_4e19af99-b231-416a-9e48-aac682306dfe" xlink:href="fsbc-20250630.xsd#fsbc_UnvestedRestrictedShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_fsbc_UnvestedRestrictedShares_4e19af99-b231-416a-9e48-aac682306dfe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUnvestedWeightedAverageRemainingContractualTerms_a3224d77-b4fc-45ab-9a89-70b7b846f83a" xlink:href="fsbc-20250630.xsd#fsbc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUnvestedWeightedAverageRemainingContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_402691ba-0cac-4309-8da4-96446b1d1403" xlink:to="loc_fsbc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUnvestedWeightedAverageRemainingContractualTerms_a3224d77-b4fc-45ab-9a89-70b7b846f83a" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/ShareholdersEquitySummaryofUnvestedSharesActivityDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#ShareholdersEquitySummaryofUnvestedSharesActivityDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/ShareholdersEquitySummaryofUnvestedSharesActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_161c74d1-b9ee-4349-ac49-aaf9877893ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cb5b9b22-6e0b-4a80-bf3e-3f562fe412f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_161c74d1-b9ee-4349-ac49-aaf9877893ce" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cb5b9b22-6e0b-4a80-bf3e-3f562fe412f6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_f63067e2-1654-4621-b20b-f3a5afff1882" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_cb5b9b22-6e0b-4a80-bf3e-3f562fe412f6" xlink:to="loc_us-gaap_AwardTypeAxis_f63067e2-1654-4621-b20b-f3a5afff1882" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f63067e2-1654-4621-b20b-f3a5afff1882_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_f63067e2-1654-4621-b20b-f3a5afff1882" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f63067e2-1654-4621-b20b-f3a5afff1882_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a309d2f0-533f-48b9-af1f-c2006c5f776b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_f63067e2-1654-4621-b20b-f3a5afff1882" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a309d2f0-533f-48b9-af1f-c2006c5f776b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_896162e2-6336-46ea-ae53-d7533bdfb093" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a309d2f0-533f-48b9-af1f-c2006c5f776b" xlink:to="loc_us-gaap_RestrictedStockMember_896162e2-6336-46ea-ae53-d7533bdfb093" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_161c74d1-b9ee-4349-ac49-aaf9877893ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_215ce524-fc06-4181-a3e6-516dd46d85c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_215ce524-fc06-4181-a3e6-516dd46d85c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_8e0d7641-5134-4806-ad48-99284cddb916" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_8e0d7641-5134-4806-ad48-99284cddb916" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_8713d0d6-c944-467c-921a-d7109093e188" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_8713d0d6-c944-467c-921a-d7109093e188" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_f1fe1a17-4c38-4dde-8552-9cca540e75f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7682a1aa-d31a-4fb8-83dd-0283ff461e89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_f1fe1a17-4c38-4dde-8552-9cca540e75f0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_dc7dc275-868a-48f0-8ec6-671558e8a62e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_161c74d1-b9ee-4349-ac49-aaf9877893ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_6c2538e9-fb90-4572-be51-acda3d265fff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_6c2538e9-fb90-4572-be51-acda3d265fff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_4c7f92ab-4f7e-4010-8935-e99190bded22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_4c7f92ab-4f7e-4010-8935-e99190bded22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_1c6d6ec1-deda-4bbe-b4e0-8e656fc311f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_1c6d6ec1-deda-4bbe-b4e0-8e656fc311f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_1da62b94-2c07-4de6-8576-c6a2863fa46a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_a58399a3-6854-433c-82c5-dd1ef41710d8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_1da62b94-2c07-4de6-8576-c6a2863fa46a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_6aceed22-8450-46bc-99b5-915af072c2f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/CommitmentsandContingenciesUnfundedLoanCommitmentsandStandbyLettersofCreditDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#CommitmentsandContingenciesUnfundedLoanCommitmentsandStandbyLettersofCreditDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/CommitmentsandContingenciesUnfundedLoanCommitmentsandStandbyLettersofCreditDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_c373c9b1-9ddb-41c4-a472-c893fb983aa0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_59e1f1e5-bb91-42e0-b18e-37f08f85fbb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_c373c9b1-9ddb-41c4-a472-c893fb983aa0" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_59e1f1e5-bb91-42e0-b18e-37f08f85fbb5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_59e1f1e5-bb91-42e0-b18e-37f08f85fbb5" xlink:to="loc_us-gaap_OtherCommitmentsAxis_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2" xlink:to="loc_us-gaap_OtherCommitmentsDomain_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_2ce15ea6-7a56-4b3a-a371-2b60445d8ae2" xlink:to="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_CommercialLinesOfCreditMember_b4ed9595-0560-492f-92ba-31a1fc165fae" xlink:href="fsbc-20250630.xsd#fsbc_CommercialLinesOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_CommercialLinesOfCreditMember_b4ed9595-0560-492f-92ba-31a1fc165fae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_UndisbursedCommercialRealEstateLoansMember_5b9ff956-24fc-44d7-b9f3-dd3ce762641e" xlink:href="fsbc-20250630.xsd#fsbc_UndisbursedCommercialRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_UndisbursedCommercialRealEstateLoansMember_5b9ff956-24fc-44d7-b9f3-dd3ce762641e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_UndisbursedConstructionLoansMember_51edc185-19e1-4b96-8790-5fcaacf1da65" xlink:href="fsbc-20250630.xsd#fsbc_UndisbursedConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_UndisbursedConstructionLoansMember_51edc185-19e1-4b96-8790-5fcaacf1da65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_AgriculturalLinesOfCreditMember_1f65d72f-069a-4a6c-b053-d1ea8d085ab1" xlink:href="fsbc-20250630.xsd#fsbc_AgriculturalLinesOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_AgriculturalLinesOfCreditMember_1f65d72f-069a-4a6c-b053-d1ea8d085ab1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_UndisbursedResidentialRealEstateLoansMember_a1dc6546-5805-43db-9d81-8e63f8d2e8f3" xlink:href="fsbc-20250630.xsd#fsbc_UndisbursedResidentialRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_UndisbursedResidentialRealEstateLoansMember_a1dc6546-5805-43db-9d81-8e63f8d2e8f3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_UndisbursedAgriculturalRealEstateLoansMember_b7cb4662-9b49-4d5e-b87f-f566198c885b" xlink:href="fsbc-20250630.xsd#fsbc_UndisbursedAgriculturalRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_UndisbursedAgriculturalRealEstateLoansMember_b7cb4662-9b49-4d5e-b87f-f566198c885b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_OtherCommitmentsMember_09720b08-8079-44d7-876e-15d2706b0f5e" xlink:href="fsbc-20250630.xsd#fsbc_OtherCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_8a13bd04-c03c-46a3-b878-8461f4201d09" xlink:to="loc_fsbc_OtherCommitmentsMember_09720b08-8079-44d7-876e-15d2706b0f5e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_64ee73ac-f393-4a5c-8dfb-c79edef0e5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_c373c9b1-9ddb-41c4-a472-c893fb983aa0" xlink:to="loc_us-gaap_OtherCommitment_64ee73ac-f393-4a5c-8dfb-c79edef0e5b1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_d7c9ee37-b458-461b-b29b-e2c43ba61e05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_us-gaap_OtherCommitmentsTable_d7c9ee37-b458-461b-b29b-e2c43ba61e05" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_d7c9ee37-b458-461b-b29b-e2c43ba61e05" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_566d78f7-acf2-4554-9369-a3e2e3449cfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_782a1ae2-c598-48dd-827d-dcc3c6f8cb3b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_566d78f7-acf2-4554-9369-a3e2e3449cfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnfundedLoanCommitmentMember_409fdffe-9c3a-4ec1-a3bd-4be55b74d113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnfundedLoanCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_566d78f7-acf2-4554-9369-a3e2e3449cfb" xlink:to="loc_us-gaap_UnfundedLoanCommitmentMember_409fdffe-9c3a-4ec1-a3bd-4be55b74d113" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_6389fb98-a0a7-4172-8da7-e8259afd8ea6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_6389fb98-a0a7-4172-8da7-e8259afd8ea6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_RealEstateRelatedLoansPercentage_6d398b0f-e54e-4466-a418-9c9883566324" xlink:href="fsbc-20250630.xsd#fsbc_RealEstateRelatedLoansPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_RealEstateRelatedLoansPercentage_6d398b0f-e54e-4466-a418-9c9883566324" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_Deposits5MillionOrMoreNumberOfDepositRelationships_04fd662b-4f6e-43ce-9e54-4e7bf0ab3e5d" xlink:href="fsbc-20250630.xsd#fsbc_Deposits5MillionOrMoreNumberOfDepositRelationships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_Deposits5MillionOrMoreNumberOfDepositRelationships_04fd662b-4f6e-43ce-9e54-4e7bf0ab3e5d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_Deposits5MillionOrMorePerDeposit_1a829c93-2f44-40b2-aca9-0bd34a7c2abe" xlink:href="fsbc-20250630.xsd#fsbc_Deposits5MillionOrMorePerDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_Deposits5MillionOrMorePerDeposit_1a829c93-2f44-40b2-aca9-0bd34a7c2abe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_Deposits5MillionOrMoreAmount_eebf885c-cc39-4f85-bf60-cf1201d53039" xlink:href="fsbc-20250630.xsd#fsbc_Deposits5MillionOrMoreAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_Deposits5MillionOrMoreAmount_eebf885c-cc39-4f85-bf60-cf1201d53039" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_PercentageOfDepositsOver5MillionToDeposits_bf97a1d5-9999-4f13-88f5-d1dd07e05176" xlink:href="fsbc-20250630.xsd#fsbc_PercentageOfDepositsOver5MillionToDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_PercentageOfDepositsOver5MillionToDeposits_bf97a1d5-9999-4f13-88f5-d1dd07e05176" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_LargestSingleDeposit_a6f2cb25-1228-42eb-b423-5703d89b0f43" xlink:href="fsbc-20250630.xsd#fsbc_LargestSingleDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_LargestSingleDeposit_a6f2cb25-1228-42eb-b423-5703d89b0f43" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_PercentageOfLargestSingleDepositToDeposits_a67ac285-22df-429a-84c1-4b45274cec2d" xlink:href="fsbc-20250630.xsd#fsbc_PercentageOfLargestSingleDepositToDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_PercentageOfLargestSingleDepositToDeposits_a67ac285-22df-429a-84c1-4b45274cec2d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashUninsuredAmount_5223d147-2dc3-4e32-8575-aebf18513a82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashUninsuredAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_us-gaap_CashUninsuredAmount_5223d147-2dc3-4e32-8575-aebf18513a82" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_fsbc_EquityMethodInvestmentRemainingCommitmentAmount_96ad09c5-4fec-4e15-b449-4d02918f9613" xlink:href="fsbc-20250630.xsd#fsbc_EquityMethodInvestmentRemainingCommitmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_4a61c8e1-484a-4431-9615-033d148fc4a3" xlink:to="loc_fsbc_EquityMethodInvestmentRemainingCommitmentAmount_96ad09c5-4fec-4e15-b449-4d02918f9613" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fivestarbank.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="fsbc-20250630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://fivestarbank.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_b3a5333f-3070-4e58-9843-62ab6f9751c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_61da5cd8-f3d4-4550-933d-7917f31b6748" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_b3a5333f-3070-4e58-9843-62ab6f9751c8" xlink:to="loc_us-gaap_SubsequentEventTable_61da5cd8-f3d4-4550-933d-7917f31b6748" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_afcb4bbd-861f-4f0b-932c-d99edc5b79b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_61da5cd8-f3d4-4550-933d-7917f31b6748" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_afcb4bbd-861f-4f0b-932c-d99edc5b79b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_afcb4bbd-861f-4f0b-932c-d99edc5b79b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_afcb4bbd-861f-4f0b-932c-d99edc5b79b1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_afcb4bbd-861f-4f0b-932c-d99edc5b79b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_529e2869-1c52-402c-a5f9-7112ca3b2022" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_afcb4bbd-861f-4f0b-932c-d99edc5b79b1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_529e2869-1c52-402c-a5f9-7112ca3b2022" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_628939af-227b-48a0-8981-b9e5dc3cb877" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_529e2869-1c52-402c-a5f9-7112ca3b2022" xlink:to="loc_us-gaap_SubsequentEventMember_628939af-227b-48a0-8981-b9e5dc3cb877" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_48853aae-c4b9-4ab7-8538-469544bca850" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_b3a5333f-3070-4e58-9843-62ab6f9751c8" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_48853aae-c4b9-4ab7-8538-469544bca850" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
