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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:0c0aa9f4-823d-48d8-bffe-39a35b710b1e,g:712df479-c3c0-4223-aaf7-63f23c40f58f-->
<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://www.southside.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITYUNAUDITED" xlink:type="simple" xlink:href="sbsi-20230331.xsd#CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITYUNAUDITED"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITYUNAUDITED" xlink:type="extended" id="i24285a19a52946cca1caa215c6679925_CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITYUNAUDITED">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1449d77a-5731-4d5a-b82d-84c7e757e402" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1449d77a-5731-4d5a-b82d-84c7e757e402" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_9ccc182a-bfa8-42a2-b72a-4d97f4ff5208" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_StockholdersEquity_9ccc182a-bfa8-42a2-b72a-4d97f4ff5208" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_9f121f60-b312-410b-87a4-36f3ecb0d567" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_NetIncomeLoss_9f121f60-b312-410b-87a4-36f3ecb0d567" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_1cfa5c7c-a2db-4662-b2d8-704958aa50f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_1cfa5c7c-a2db-4662-b2d8-704958aa50f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_992524c0-0a04-4879-ba2d-f9b6c8d0be8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_992524c0-0a04-4879-ba2d-f9b6c8d0be8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fa295218-bab0-4a3c-baff-c8b0d5f0c271" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fa295218-bab0-4a3c-baff-c8b0d5f0c271" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7231f7f4-c6b9-4e30-859d-1259483c8084" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7231f7f4-c6b9-4e30-859d-1259483c8084" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_dbbb7640-cbd5-483f-8e0e-77eba7d9cb49" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_dbbb7640-cbd5-483f-8e0e-77eba7d9cb49" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_56bf418d-c49c-4397-a7b4-227eced16c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_542dc263-ed5b-4680-8ab2-8c57f573fca7" xlink:to="loc_us-gaap_DividendsCommonStockCash_56bf418d-c49c-4397-a7b4-227eced16c4d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_6a44ae11-9ce0-4381-9618-7c0496a09b46" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f8ba0bc1-8850-4191-b8de-e7fd8d9a930e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1449d77a-5731-4d5a-b82d-84c7e757e402" xlink:to="loc_us-gaap_StatementTable_f8ba0bc1-8850-4191-b8de-e7fd8d9a930e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f8ba0bc1-8850-4191-b8de-e7fd8d9a930e" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9" xlink:to="loc_us-gaap_EquityComponentDomain_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_64989d6f-dc7a-44c0-9dde-a9ab0ce51cf9" xlink:to="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_920b8250-8a02-493a-8dc4-aed21c09d3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:to="loc_us-gaap_CommonStockMember_920b8250-8a02-493a-8dc4-aed21c09d3a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_a32e43e6-115c-4e4d-a329-9eb32f8cac8f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_a32e43e6-115c-4e4d-a329-9eb32f8cac8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_cdab2d4b-5aa4-4a08-aa44-3b85e0def6cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:to="loc_us-gaap_RetainedEarningsMember_cdab2d4b-5aa4-4a08-aa44-3b85e0def6cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_c736ebcc-9960-4811-94d0-f619ae09e20e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:to="loc_us-gaap_TreasuryStockMember_c736ebcc-9960-4811-94d0-f619ae09e20e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_33cae65c-c45a-406f-9bf6-ac14e424d482" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_583ec43f-f227-464f-b162-35d7309da748" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_33cae65c-c45a-406f-9bf6-ac14e424d482" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeChangesInDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeChangesInDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeChangesInDetails" xlink:type="extended" id="ia84474e1f8f54ffebccd3a2a42317ddb_AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeChangesInDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_884d3084-b2e8-441c-9161-463c343d8152" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_884d3084-b2e8-441c-9161-463c343d8152" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b1606b0f-e052-4eaa-a8ba-713dfd1535a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:to="loc_us-gaap_StockholdersEquity_b1606b0f-e052-4eaa-a8ba-713dfd1535a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_fe8274c2-7b66-44b9-85b0-c4ecde05698e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_fe8274c2-7b66-44b9-85b0-c4ecde05698e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_d0f462da-3334-40f3-9eb6-ddb401eed076" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_d0f462da-3334-40f3-9eb6-ddb401eed076" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_daa0eab3-10b8-4436-ad20-40e5a201734f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_daa0eab3-10b8-4436-ad20-40e5a201734f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_79404b49-cc13-4ef4-a564-982e292badf8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_8c06a911-93e1-4e72-892a-a90991e65a39" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_79404b49-cc13-4ef4-a564-982e292badf8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_8c5574ef-5ced-4346-8513-2fbc385b9cb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_85a8faf0-9fae-45b8-865a-000e30e5da97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_884d3084-b2e8-441c-9161-463c343d8152" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_85a8faf0-9fae-45b8-865a-000e30e5da97" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_4f570315-4bec-4352-a8df-72e4f69fe505" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_85a8faf0-9fae-45b8-865a-000e30e5da97" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_4f570315-4bec-4352-a8df-72e4f69fe505" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_4f570315-4bec-4352-a8df-72e4f69fe505_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_4f570315-4bec-4352-a8df-72e4f69fe505" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_4f570315-4bec-4352-a8df-72e4f69fe505_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_ca74f6b5-0bf0-440f-bcd5-475b6a451971" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_4f570315-4bec-4352-a8df-72e4f69fe505" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_ca74f6b5-0bf0-440f-bcd5-475b6a451971" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_1fcbb724-02a3-46e8-99be-38fa08428d2f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_ca74f6b5-0bf0-440f-bcd5-475b6a451971" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_1fcbb724-02a3-46e8-99be-38fa08428d2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_85a8faf0-9fae-45b8-865a-000e30e5da97" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1" xlink:to="loc_us-gaap_EquityComponentDomain_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0af5adc6-7ece-41ce-9ad3-85bd71eab5e1" xlink:to="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_e4ddc022-5587-4d34-95be-c2cc1681753c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_e4ddc022-5587-4d34-95be-c2cc1681753c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_91064840-049f-42bc-991b-bd2e6ec0948f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_91064840-049f-42bc-991b-bd2e6ec0948f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_ed06c652-b271-4f0e-b39c-18b42ee55cc1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_ed06c652-b271-4f0e-b39c-18b42ee55cc1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b2d7c81a-d76e-4b32-a7f4-c13ef79d012c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_bae39fa6-e070-40f1-b23d-de05495af5b5" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b2d7c81a-d76e-4b32-a7f4-c13ef79d012c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/AccumulatedOtherComprehensiveIncomeLossReclassificationsoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#AccumulatedOtherComprehensiveIncomeLossReclassificationsoutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/AccumulatedOtherComprehensiveIncomeLossReclassificationsoutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i5ec7436c32794cc2a16905c7963139b0_AccumulatedOtherComprehensiveIncomeLossReclassificationsoutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax_2f3b0084-81df-42d2-8377-4c333a95d29d" xlink:href="sbsi-20230331.xsd#sbsi_AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_sbsi_AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax_2f3b0084-81df-42d2-8377-4c333a95d29d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_53e825c6-37f5-45b3-ba84-d42ca24ca7a3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_53e825c6-37f5-45b3-ba84-d42ca24ca7a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_4a9753e6-b7ff-4392-b30c-8ab35334b7a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_4a9753e6-b7ff-4392-b30c-8ab35334b7a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_fc90984b-2a11-48fb-9afd-2cd5acc2f730" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_fc90984b-2a11-48fb-9afd-2cd5acc2f730" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_8dff534e-3a00-4c90-ad87-28a423375971" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_8dff534e-3a00-4c90-ad87-28a423375971" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_8b6fdeed-43c0-4ed5-8ce1-b6e1534c4b3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_8b6fdeed-43c0-4ed5-8ce1-b6e1534c4b3c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_c9e01844-53c7-4991-8324-b5a70d43eed5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_c9e01844-53c7-4991-8324-b5a70d43eed5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_491380dd-f227-481d-8ae2-2e125c06b902" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_491380dd-f227-481d-8ae2-2e125c06b902" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_b1b7a7fc-79a9-4222-acc8-0128aec5ed5d" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_2dcc25e2-fdb3-45ae-a349-b2d5875004e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_2dcc25e2-fdb3-45ae-a349-b2d5875004e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_2dcc25e2-fdb3-45ae-a349-b2d5875004e5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2dcc25e2-fdb3-45ae-a349-b2d5875004e5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_2dcc25e2-fdb3-45ae-a349-b2d5875004e5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_76f4bf3a-5b61-41b9-b318-15d1bf70cc19" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2dcc25e2-fdb3-45ae-a349-b2d5875004e5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_76f4bf3a-5b61-41b9-b318-15d1bf70cc19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_0acaabaf-1719-4452-845e-f93975f41196" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_76f4bf3a-5b61-41b9-b318-15d1bf70cc19" xlink:to="loc_us-gaap_InterestRateSwapMember_0acaabaf-1719-4452-845e-f93975f41196" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8d77131a-745f-44d3-b096-8929a4b0848c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InformationByCategoryOfDebtSecurityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:to="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8d77131a-745f-44d3-b096-8929a4b0848c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_8d77131a-745f-44d3-b096-8929a4b0848c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8d77131a-745f-44d3-b096-8929a4b0848c" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_8d77131a-745f-44d3-b096-8929a4b0848c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_b4721aea-0217-4264-ace5-9dde59ff12f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8d77131a-745f-44d3-b096-8929a4b0848c" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_b4721aea-0217-4264-ace5-9dde59ff12f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SecuritiesTransferredBetweenHeldtoMaturityAndAvailableforSaleSecuritiesMember_660a3df7-c642-41f3-bea9-86ffe85e54be" xlink:href="sbsi-20230331.xsd#sbsi_SecuritiesTransferredBetweenHeldtoMaturityAndAvailableforSaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_b4721aea-0217-4264-ace5-9dde59ff12f6" xlink:to="loc_sbsi_SecuritiesTransferredBetweenHeldtoMaturityAndAvailableforSaleSecuritiesMember_660a3df7-c642-41f3-bea9-86ffe85e54be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_dbbc1f19-497d-4be4-bff6-c7383dbe392c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableforsaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_b4721aea-0217-4264-ace5-9dde59ff12f6" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_dbbc1f19-497d-4be4-bff6-c7383dbe392c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5ea33623-be8b-4dc2-9a59-d281532c7080" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5ea33623-be8b-4dc2-9a59-d281532c7080" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5ea33623-be8b-4dc2-9a59-d281532c7080_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5ea33623-be8b-4dc2-9a59-d281532c7080" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5ea33623-be8b-4dc2-9a59-d281532c7080_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_34072fa5-7d1f-4311-a883-87de05ba0570" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5ea33623-be8b-4dc2-9a59-d281532c7080" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_34072fa5-7d1f-4311-a883-87de05ba0570" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_a57039df-9d03-45ed-ab67-5cb3d69816e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_34072fa5-7d1f-4311-a883-87de05ba0570" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_a57039df-9d03-45ed-ab67-5cb3d69816e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_338e62c1-f005-4c63-8f2e-d5402d410774" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_aa679c8f-809a-41cc-814b-7dfad613d2f4" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_338e62c1-f005-4c63-8f2e-d5402d410774" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_338e62c1-f005-4c63-8f2e-d5402d410774_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_338e62c1-f005-4c63-8f2e-d5402d410774" xlink:to="loc_us-gaap_EquityComponentDomain_338e62c1-f005-4c63-8f2e-d5402d410774_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_338e62c1-f005-4c63-8f2e-d5402d410774" xlink:to="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_50bce310-de4c-4e73-86d9-014764854a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_50bce310-de4c-4e73-86d9-014764854a4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_f84e4a7c-e1ff-4288-aa98-e9cbe2494fc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_f84e4a7c-e1ff-4288-aa98-e9cbe2494fc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_f4afbf24-6560-4b7f-9519-51ddf70a869e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_f4afbf24-6560-4b7f-9519-51ddf70a869e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_3899a19a-3b99-47f0-bba6-3db9f479026f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5377ebae-8798-425b-9aa2-cd78dd33e3bb" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_3899a19a-3b99-47f0-bba6-3db9f479026f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/SecuritiesScheduleofDebtSecuritiesComponentsDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#SecuritiesScheduleofDebtSecuritiesComponentsDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/SecuritiesScheduleofDebtSecuritiesComponentsDetails" xlink:type="extended" id="i71d2074744164c9c83c309b918886530_SecuritiesScheduleofDebtSecuritiesComponentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_62e4d8e3-f193-4772-b950-38b65753fcb1" xlink:href="sbsi-20230331.xsd#sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_62e4d8e3-f193-4772-b950-38b65753fcb1" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_522bcf06-5267-405b-b604-767c88be75b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_522bcf06-5267-405b-b604-767c88be75b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_59278726-2477-4f07-9502-fdac9872132f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_59278726-2477-4f07-9502-fdac9872132f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_607f9d96-6f6c-4763-8d41-fc9433680107" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_607f9d96-6f6c-4763-8d41-fc9433680107" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_4e25f56c-6343-4720-9bce-c242c07f4d31" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_a9f16a9f-c4bd-40fd-87b0-2c3f7b3ef14d" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_4e25f56c-6343-4720-9bce-c242c07f4d31" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesClassifiedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_62e4d8e3-f193-4772-b950-38b65753fcb1" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_714a2fd0-1bea-443f-acbf-ca635c1f2195" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_714a2fd0-1bea-443f-acbf-ca635c1f2195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_44d98341-4057-40fd-b751-1f9669ec12a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_44d98341-4057-40fd-b751-1f9669ec12a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_a24094b4-05f9-4ab1-864b-c6d5e28d1b98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_a24094b4-05f9-4ab1-864b-c6d5e28d1b98" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_1255e86f-800b-469a-94ca-c1d6b8d274c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_7afd10f6-c504-42c4-a2d8-7911a45ad9c8" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_1255e86f-800b-469a-94ca-c1d6b8d274c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_c092831e-279d-451c-a4a5-27fb35426456" xlink:href="sbsi-20230331.xsd#sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_62e4d8e3-f193-4772-b950-38b65753fcb1" xlink:to="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_c092831e-279d-451c-a4a5-27fb35426456" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_7f761eb8-b82f-4be9-b6a7-a16cb4021bff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_c092831e-279d-451c-a4a5-27fb35426456" xlink:to="loc_us-gaap_FinancialInstrumentAxis_7f761eb8-b82f-4be9-b6a7-a16cb4021bff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7f761eb8-b82f-4be9-b6a7-a16cb4021bff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_7f761eb8-b82f-4be9-b6a7-a16cb4021bff" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7f761eb8-b82f-4be9-b6a7-a16cb4021bff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_7f761eb8-b82f-4be9-b6a7-a16cb4021bff" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_8a75c575-840a-4629-8a61-1f2f63605a62" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_8a75c575-840a-4629-8a61-1f2f63605a62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_643fd38d-2b81-4fff-9f98-2b76624d8afe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_643fd38d-2b81-4fff-9f98-2b76624d8afe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_c06bf8c5-7f68-4f57-b184-70f2b88d786f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_c06bf8c5-7f68-4f57-b184-70f2b88d786f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_8ecc6b7d-8886-4689-b75c-8d947715e542" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_8ecc6b7d-8886-4689-b75c-8d947715e542" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_965b8ffe-1e8a-4c3c-a340-455b08467e43" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4bb48ac8-5322-4d26-a306-5e710cb26149" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_965b8ffe-1e8a-4c3c-a340-455b08467e43" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/SecuritiesUnrealizedLossonSecuritiesDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#SecuritiesUnrealizedLossonSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/SecuritiesUnrealizedLossonSecuritiesDetails" xlink:type="extended" id="i867909e44cd24d79bb6dc325e3174698_SecuritiesUnrealizedLossonSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_4dfb62a5-ec3d-41d9-89fe-da974499bace" xlink:href="sbsi-20230331.xsd#sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_4dfb62a5-ec3d-41d9-89fe-da974499bace" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_f8649f99-9ae1-4fb8-aaf9-47391909d7ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_f8649f99-9ae1-4fb8-aaf9-47391909d7ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_1dc3da17-e59d-439d-8a37-330902f60de1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_1dc3da17-e59d-439d-8a37-330902f60de1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_4c899477-c805-46c2-a13d-b6c52a0adfbc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_4c899477-c805-46c2-a13d-b6c52a0adfbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_06c5baa0-4fde-4993-ade6-df96a72a97ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_06c5baa0-4fde-4993-ade6-df96a72a97ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_9c44b67a-a7d4-4bb3-8767-0b93c30fdb87" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_9c44b67a-a7d4-4bb3-8767-0b93c30fdb87" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_d3aec9eb-98de-4b66-8d20-a89b960ce065" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract_2bd681d1-8fda-45df-8b5e-42f2fd5f68cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_d3aec9eb-98de-4b66-8d20-a89b960ce065" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_4dfb62a5-ec3d-41d9-89fe-da974499bace" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_62655018-d8ef-4dbb-bb0f-238605b3d8c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_62655018-d8ef-4dbb-bb0f-238605b3d8c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_07076cfe-baad-45f6-a19c-48130be7ad31" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_07076cfe-baad-45f6-a19c-48130be7ad31" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_b9db0826-bbbc-416c-92a8-a8497396c660" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_b9db0826-bbbc-416c-92a8-a8497396c660" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_2de55a7f-a1b0-4d1f-b23e-9b561fabad34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_2de55a7f-a1b0-4d1f-b23e-9b561fabad34" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_734f35a5-7428-477c-a85a-e78f7d5cbc8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_734f35a5-7428-477c-a85a-e78f7d5cbc8a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_5e5c4b2c-9f97-43e4-a490-5097fb19644e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesTransferredSecurityUnrealizedGainLossAbstract_fbc33ac3-3d7b-4b02-bad4-1a2b1fe29334" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_5e5c4b2c-9f97-43e4-a490-5097fb19644e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_d3b66c92-4bf1-4624-9e57-424393de5cfb" xlink:href="sbsi-20230331.xsd#sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesLineItems_4dfb62a5-ec3d-41d9-89fe-da974499bace" xlink:to="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_d3b66c92-4bf1-4624-9e57-424393de5cfb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_c5fb1f67-9b6b-415b-9b36-112315463131" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesTable_d3b66c92-4bf1-4624-9e57-424393de5cfb" xlink:to="loc_us-gaap_FinancialInstrumentAxis_c5fb1f67-9b6b-415b-9b36-112315463131" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c5fb1f67-9b6b-415b-9b36-112315463131_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c5fb1f67-9b6b-415b-9b36-112315463131" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c5fb1f67-9b6b-415b-9b36-112315463131_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c5fb1f67-9b6b-415b-9b36-112315463131" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_cbdf8e2a-1aa0-4499-b84d-337f7ea24214" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_cbdf8e2a-1aa0-4499-b84d-337f7ea24214" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_b23353c0-5ac3-4fc2-8664-d4b809f52930" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_b23353c0-5ac3-4fc2-8664-d4b809f52930" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_1b7c881e-740c-4476-9abf-01e83f494bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_1b7c881e-740c-4476-9abf-01e83f494bf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_7658cabf-5323-482c-a7b6-2fb96c798615" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_7658cabf-5323-482c-a7b6-2fb96c798615" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_ea41a615-8e11-42f1-b1d9-090bb93926dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d716b550-c752-4ff6-9ea8-ea2443ee6aa7" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_ea41a615-8e11-42f1-b1d9-090bb93926dd" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/SecuritiesNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#SecuritiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/SecuritiesNarrativeDetails" xlink:type="extended" id="i432a90ed88d14c48aff70e80091c266d_SecuritiesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss_7819c3e1-040e-4462-976b-5743ce94b593" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss_7819c3e1-040e-4462-976b-5743ce94b593" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_TransferredSecuritiesUnrealizedLossBeforeTax_cd2966ca-c189-4407-ad95-12b1ec2e2819" xlink:href="sbsi-20230331.xsd#sbsi_TransferredSecuritiesUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_sbsi_TransferredSecuritiesUnrealizedLossBeforeTax_cd2966ca-c189-4407-ad95-12b1ec2e2819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SecuritiesTransferredUnrealizedLossNetOfTax_6e0171d1-975c-4e16-89aa-d7492207cae1" xlink:href="sbsi-20230331.xsd#sbsi_SecuritiesTransferredUnrealizedLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_sbsi_SecuritiesTransferredUnrealizedLossNetOfTax_6e0171d1-975c-4e16-89aa-d7492207cae1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SecuritiesTransferredFromAvailableForSaleToHeldToMaturity_79c50f05-c316-46e0-87d9-72e5df6fccf3" xlink:href="sbsi-20230331.xsd#sbsi_SecuritiesTransferredFromAvailableForSaleToHeldToMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_sbsi_SecuritiesTransferredFromAvailableForSaleToHeldToMaturity_79c50f05-c316-46e0-87d9-72e5df6fccf3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_70c5f537-9db5-4226-a764-3717854fca04" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_70c5f537-9db5-4226-a764-3717854fca04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGain_e29bda20-5fef-4ca1-8660-ba2f142c45bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGain_e29bda20-5fef-4ca1-8660-ba2f142c45bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss_4c564c02-76e5-4cfd-86d5-11090ec44888" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss_4c564c02-76e5-4cfd-86d5-11090ec44888" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue_8e498175-f74c-459e-84cf-ad2cdd1d2023" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract_20906845-27cd-4487-b91e-f225a2276308" xlink:to="loc_us-gaap_EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue_8e498175-f74c-459e-84cf-ad2cdd1d2023" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfHeldToMaturitySecurities_d166e1df-7893-4c36-b255-e6f29e37385e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromSaleOfHeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:to="loc_us-gaap_ProceedsFromSaleOfHeldToMaturitySecurities_d166e1df-7893-4c36-b255-e6f29e37385e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivable_1c9cdb6e-4c4f-448f-bd17-d2265c1a56d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:to="loc_us-gaap_InterestReceivable_1c9cdb6e-4c4f-448f-bd17-d2265c1a56d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityNonaccrual_41979e7a-8697-4071-9c04-8d51512a0de0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesHeldToMaturityNonaccrual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityNonaccrual_41979e7a-8697-4071-9c04-8d51512a0de0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalHomeLoanBankStockWithOtherThanTemporaryImpairment_c9128a88-1cc9-46ad-bbc6-836d6cdb87e3" xlink:href="sbsi-20230331.xsd#sbsi_FederalHomeLoanBankStockWithOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:to="loc_sbsi_FederalHomeLoanBankStockWithOtherThanTemporaryImpairment_c9128a88-1cc9-46ad-bbc6-836d6cdb87e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_OtherThanTemporarilyImpairedEquityInvestments_ffd724f3-5444-4c9c-b6bd-93c20f149078" xlink:href="sbsi-20230331.xsd#sbsi_OtherThanTemporarilyImpairedEquityInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesSalesOrTransfersOfInvestmentsAbstract_77038ec8-0ee9-45e8-9d54-d81e48217da1" xlink:to="loc_sbsi_OtherThanTemporarilyImpairedEquityInvestments_ffd724f3-5444-4c9c-b6bd-93c20f149078" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_7ef2054c-9033-4b3d-8745-1bf68bc12e89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_HeldToMaturitySecurities_7ef2054c-9033-4b3d-8745-1bf68bc12e89" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_4d6d1524-db08-498b-9d51-14b4c878b69e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_4d6d1524-db08-498b-9d51-14b4c878b69e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecurities_e4ab9d97-815c-47a0-a9a6-04a91339b361" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_DebtSecurities_e4ab9d97-815c-47a0-a9a6-04a91339b361" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestCreditLossExpenseReversal_41dc8804-c4fa-499e-9cf0-48e4055d71ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestCreditLossExpenseReversal_41dc8804-c4fa-499e-9cf0-48e4055d71ed" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_6d0dab61-6d4e-498e-a39a-2b09180f2851" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_6d0dab61-6d4e-498e-a39a-2b09180f2851" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_EquitySecuritiesRealizedGain_932b31aa-3e97-4b7e-a2f5-26ce1a90cae0" xlink:href="sbsi-20230331.xsd#sbsi_EquitySecuritiesRealizedGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_sbsi_EquitySecuritiesRealizedGain_932b31aa-3e97-4b7e-a2f5-26ce1a90cae0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_669ffda8-88ab-49b3-a55b-097cbd55b8c1" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_358edc63-bfef-45f8-9e1c-305605f32820" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InformationByCategoryOfDebtSecurityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:to="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_358edc63-bfef-45f8-9e1c-305605f32820" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_358edc63-bfef-45f8-9e1c-305605f32820_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_358edc63-bfef-45f8-9e1c-305605f32820" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_358edc63-bfef-45f8-9e1c-305605f32820_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_26fadc0e-c236-47b0-9eb4-3ed61a068a37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_358edc63-bfef-45f8-9e1c-305605f32820" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_26fadc0e-c236-47b0-9eb4-3ed61a068a37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_61f65410-4343-49e6-a284-2705cf261735" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableforsaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_26fadc0e-c236-47b0-9eb4-3ed61a068a37" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_61f65410-4343-49e6-a284-2705cf261735" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesMember_0815e221-300e-4c33-94be-3f3eaa8948dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HeldtomaturitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_26fadc0e-c236-47b0-9eb4-3ed61a068a37" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesMember_0815e221-300e-4c33-94be-3f3eaa8948dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_2f655dae-81bd-4250-99c7-9bb837eba971" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_2f655dae-81bd-4250-99c7-9bb837eba971" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_2f655dae-81bd-4250-99c7-9bb837eba971_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_2f655dae-81bd-4250-99c7-9bb837eba971" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_2f655dae-81bd-4250-99c7-9bb837eba971_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_b9a85b85-8939-48d7-8d39-e796d9ef5136" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_2f655dae-81bd-4250-99c7-9bb837eba971" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_b9a85b85-8939-48d7-8d39-e796d9ef5136" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetPastDueMember_d72ab05e-dc18-454b-af0e-a3dd0a879730" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialAssetPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_b9a85b85-8939-48d7-8d39-e796d9ef5136" xlink:to="loc_us-gaap_FinancialAssetPastDueMember_d72ab05e-dc18-454b-af0e-a3dd0a879730" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_fbfc0eed-682d-4632-97cd-bc0b76568b4a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:to="loc_us-gaap_PledgedStatusAxis_fbfc0eed-682d-4632-97cd-bc0b76568b4a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_fbfc0eed-682d-4632-97cd-bc0b76568b4a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_fbfc0eed-682d-4632-97cd-bc0b76568b4a" xlink:to="loc_us-gaap_PledgedStatusDomain_fbfc0eed-682d-4632-97cd-bc0b76568b4a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_a5139403-57a8-4f0e-b4bd-0809c04a1cf1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_fbfc0eed-682d-4632-97cd-bc0b76568b4a" xlink:to="loc_us-gaap_PledgedStatusDomain_a5139403-57a8-4f0e-b4bd-0809c04a1cf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralMember_1c1326f6-ca3f-422b-8459-8d016a5cb695" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetPledgedAsCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_a5139403-57a8-4f0e-b4bd-0809c04a1cf1" xlink:to="loc_us-gaap_AssetPledgedAsCollateralMember_1c1326f6-ca3f-422b-8459-8d016a5cb695" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_40050d80-901e-4e59-ae82-3c2e7109e478" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_0e88a982-97c7-4632-a7d1-7283380ab60e" xlink:to="loc_us-gaap_FinancialInstrumentAxis_40050d80-901e-4e59-ae82-3c2e7109e478" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_40050d80-901e-4e59-ae82-3c2e7109e478_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_40050d80-901e-4e59-ae82-3c2e7109e478" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_40050d80-901e-4e59-ae82-3c2e7109e478_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_87fbb897-c5b6-43c3-96d2-3bada8aeedaa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_40050d80-901e-4e59-ae82-3c2e7109e478" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_87fbb897-c5b6-43c3-96d2-3bada8aeedaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_f4bf7048-b0b8-4d95-8754-27e96b383639" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_87fbb897-c5b6-43c3-96d2-3bada8aeedaa" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_f4bf7048-b0b8-4d95-8754-27e96b383639" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_f316cfd1-d612-403e-b78a-febf1f8608fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_87fbb897-c5b6-43c3-96d2-3bada8aeedaa" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_f316cfd1-d612-403e-b78a-febf1f8608fd" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesLoansbyPortfolioSegmentDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesLoansbyPortfolioSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesLoansbyPortfolioSegmentDetails" xlink:type="extended" id="iaebe5155e47e4c62937acd3873cd3e99_LoansandAllowanceforLoanLossesLoansbyPortfolioSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_be2fee84-90fd-44e0-ac2e-94d987ca32fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansAndLeasesReceivableDisclosureAbstract_36947694-82ec-4af0-8f2c-e32df0ba54e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansAndLeasesReceivableDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_be2fee84-90fd-44e0-ac2e-94d987ca32fd" xlink:to="loc_us-gaap_LoansAndLeasesReceivableDisclosureAbstract_36947694-82ec-4af0-8f2c-e32df0ba54e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_86e0deac-bc3a-4687-bc59-f529de504c33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureAbstract_36947694-82ec-4af0-8f2c-e32df0ba54e9" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_86e0deac-bc3a-4687-bc59-f529de504c33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_fc6d2583-4df8-4cc6-a29b-0f08d854f57e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureAbstract_36947694-82ec-4af0-8f2c-e32df0ba54e9" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_fc6d2583-4df8-4cc6-a29b-0f08d854f57e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_5c59a48e-5f63-45f3-84f5-b8ddda3985c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureAbstract_36947694-82ec-4af0-8f2c-e32df0ba54e9" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_5c59a48e-5f63-45f3-84f5-b8ddda3985c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_120e32a3-4fdb-4572-ad9d-df37f8577dba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_be2fee84-90fd-44e0-ac2e-94d987ca32fd" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_120e32a3-4fdb-4572-ad9d-df37f8577dba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ce5c0858-a152-48f9-b752-389700198f7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_120e32a3-4fdb-4572-ad9d-df37f8577dba" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ce5c0858-a152-48f9-b752-389700198f7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ce5c0858-a152-48f9-b752-389700198f7a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ce5c0858-a152-48f9-b752-389700198f7a" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_ce5c0858-a152-48f9-b752-389700198f7a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_ce5c0858-a152-48f9-b752-389700198f7a" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_e04f1f9c-ba4e-4e05-9f34-605567dd75b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_us-gaap_ConstructionLoansMember_e04f1f9c-ba4e-4e05-9f34-605567dd75b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_3548387d-609f-4687-851f-16722455b7ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_us-gaap_ResidentialRealEstateMember_3548387d-609f-4687-851f-16722455b7ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_22c02bfe-4a32-4452-9a7e-77ea2ec4b7d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_22c02bfe-4a32-4452-9a7e-77ea2ec4b7d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_fb63cdde-580d-4975-83cb-e2d83e8923c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_us-gaap_CommercialLoanMember_fb63cdde-580d-4975-83cb-e2d83e8923c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MunicipalLoansMember_47168ef4-b69b-4caf-955b-b925b6e5ad9a" xlink:href="sbsi-20230331.xsd#sbsi_MunicipalLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_sbsi_MunicipalLoansMember_47168ef4-b69b-4caf-955b-b925b6e5ad9a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerLoanMember_ce870ae0-de92-466d-ade9-630595dae590" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConsumerLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b5bcbcad-4b7c-49f7-9c85-8dd52c5967bf" xlink:to="loc_us-gaap_ConsumerLoanMember_ce870ae0-de92-466d-ade9-630595dae590" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesLoansbyCreditQualityIndicatorandOriginationYearDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesLoansbyCreditQualityIndicatorandOriginationYearDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesLoansbyCreditQualityIndicatorandOriginationYearDetails" xlink:type="extended" id="i9919f1fdba944fe888edf5a4cd788521_LoansandAllowanceforLoanLossesLoansbyCreditQualityIndicatorandOriginationYearDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_a7d33b27-cc37-46b1-bb8c-55641a9f4815" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_a7d33b27-cc37-46b1-bb8c-55641a9f4815" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_6542ed22-76a5-4890-914d-feb40a850e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_6542ed22-76a5-4890-914d-feb40a850e3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_1b4ebb48-764a-4603-bba6-0df292246ae6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_1b4ebb48-764a-4603-bba6-0df292246ae6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_93104647-5ea5-4e0a-93dc-4f8c5cd78fd0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_93104647-5ea5-4e0a-93dc-4f8c5cd78fd0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_c5c2c881-1576-4e72-b623-3fef5d54ae41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_c5c2c881-1576-4e72-b623-3fef5d54ae41" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_92506181-8653-45bf-978c-ae2734c5dbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_92506181-8653-45bf-978c-ae2734c5dbe5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_8241286c-e225-4cdd-b899-17998b1d11de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_8241286c-e225-4cdd-b899-17998b1d11de" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_49bef9f8-8345-4185-96fa-fac38b24ae3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_49bef9f8-8345-4185-96fa-fac38b24ae3f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_12f7a963-c61d-437f-8317-98f593670a15" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_12f7a963-c61d-437f-8317-98f593670a15" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedCurrentFiscalYearWriteoff_e047bcb2-bef8-4884-924a-9c9bc3a49779" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedCurrentFiscalYearWriteoff_e047bcb2-bef8-4884-924a-9c9bc3a49779" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedCurrentFiscalYearWriteoff_c1480adf-cf50-4136-b511-41e1d51c30b7" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedCurrentFiscalYearWriteoff_c1480adf-cf50-4136-b511-41e1d51c30b7" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearFourOriginatedCurrentFiscalYearWriteoff_93448f86-7809-4cea-9392-db04e0b4ac5f" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestYearFourOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearFourOriginatedCurrentFiscalYearWriteoff_93448f86-7809-4cea-9392-db04e0b4ac5f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedCurrentFiscalYearWriteoff_0efe8946-fdf5-4a14-b646-dc88f58a4b46" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedCurrentFiscalYearWriteoff_0efe8946-fdf5-4a14-b646-dc88f58a4b46" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_41ba0c47-19be-4ee9-ac8c-b394e7c65425" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_41ba0c47-19be-4ee9-ac8c-b394e7c65425" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_368c5eb0-581a-4a60-ba3e-7fc17af1635e" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_368c5eb0-581a-4a60-ba3e-7fc17af1635e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_049705b7-ba79-4759-a29c-76c04f25ba31" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_049705b7-ba79-4759-a29c-76c04f25ba31" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_12283052-d5a4-41fd-a882-17c470f2ebc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_9e9bf959-8729-413b-bdad-8db8f613f850" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_12283052-d5a4-41fd-a882-17c470f2ebc5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_12283052-d5a4-41fd-a882-17c470f2ebc5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4bb2ae11-88a3-4264-969f-c27a1b0b9cb2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_8f8d216f-6eb3-4134-9618-db15b31acb25" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_us-gaap_ConstructionLoansMember_8f8d216f-6eb3-4134-9618-db15b31acb25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_46aafc04-6d19-4c7a-ae11-6ebf3790dad8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_us-gaap_ResidentialRealEstateMember_46aafc04-6d19-4c7a-ae11-6ebf3790dad8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_6c00940c-4588-4dcd-9332-1aac1f1ad467" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_6c00940c-4588-4dcd-9332-1aac1f1ad467" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_c9ef5576-660f-49b7-a2c4-d3e1fc0d06a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_us-gaap_CommercialLoanMember_c9ef5576-660f-49b7-a2c4-d3e1fc0d06a9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MunicipalLoansMember_2f36e330-4040-48e1-acef-655dedbae5f7" xlink:href="sbsi-20230331.xsd#sbsi_MunicipalLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_sbsi_MunicipalLoansMember_2f36e330-4040-48e1-acef-655dedbae5f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerLoanMember_8921a04a-b842-42df-bf35-4e5e1c81c6a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConsumerLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_us-gaap_ConsumerLoanMember_8921a04a-b842-42df-bf35-4e5e1c81c6a9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DemandDepositOverdraftsMember_9a0a3eff-bbb3-4387-8bac-fbe7d63fa515" xlink:href="sbsi-20230331.xsd#sbsi_DemandDepositOverdraftsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_05e60e23-caf5-4ad4-bd1d-778d22872e2e" xlink:to="loc_sbsi_DemandDepositOverdraftsMember_9a0a3eff-bbb3-4387-8bac-fbe7d63fa515" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_df1b4e8f-86af-4141-9a86-d991576324a3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_12283052-d5a4-41fd-a882-17c470f2ebc5" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_df1b4e8f-86af-4141-9a86-d991576324a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_df1b4e8f-86af-4141-9a86-d991576324a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_df1b4e8f-86af-4141-9a86-d991576324a3" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_df1b4e8f-86af-4141-9a86-d991576324a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_df1b4e8f-86af-4141-9a86-d991576324a3" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassMember_a239bb22-12f7-46a0-86b5-f0872a06b549" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:to="loc_us-gaap_PassMember_a239bb22-12f7-46a0-86b5-f0872a06b549" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_PassWatchMember_d2a12877-9ba5-4595-be51-f9444a2f8f4f" xlink:href="sbsi-20230331.xsd#sbsi_PassWatchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:to="loc_sbsi_PassWatchMember_d2a12877-9ba5-4595-be51-f9444a2f8f4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SpecialMentionMember_4dafdbaf-6603-4fea-a8c2-af9882bbab97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SpecialMentionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:to="loc_us-gaap_SpecialMentionMember_4dafdbaf-6603-4fea-a8c2-af9882bbab97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubstandardMember_a254289f-fa77-4134-a51c-7120e10fe0f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubstandardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:to="loc_us-gaap_SubstandardMember_a254289f-fa77-4134-a51c-7120e10fe0f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DoubtfulMember_4a8086e2-26e4-49fe-9081-6c0def997945" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DoubtfulMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_f8950bcb-818a-4a50-a3bb-461ee1d98d69" xlink:to="loc_us-gaap_DoubtfulMember_4a8086e2-26e4-49fe-9081-6c0def997945" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesAgingofPastDueLoansbyClassofLoanDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesAgingofPastDueLoansbyClassofLoanDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesAgingofPastDueLoansbyClassofLoanDetails" xlink:type="extended" id="i8a8dc82afe764e2aa1ed8f7e41cadbbd_LoansandAllowanceforLoanLossesAgingofPastDueLoansbyClassofLoanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_93d46f82-c195-498c-b444-de8e639b4328" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_9acee37c-bcec-4adc-ac47-1ca6de159805" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_93d46f82-c195-498c-b444-de8e639b4328" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_9acee37c-bcec-4adc-ac47-1ca6de159805" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_9e6a749b-c9c8-451a-9dc4-7cf46c7c4816" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_93d46f82-c195-498c-b444-de8e639b4328" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_9e6a749b-c9c8-451a-9dc4-7cf46c7c4816" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7ec0317f-886b-4916-8550-33f4bfc1a857" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_9e6a749b-c9c8-451a-9dc4-7cf46c7c4816" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7ec0317f-886b-4916-8550-33f4bfc1a857" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7ec0317f-886b-4916-8550-33f4bfc1a857_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7ec0317f-886b-4916-8550-33f4bfc1a857" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_7ec0317f-886b-4916-8550-33f4bfc1a857_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7ec0317f-886b-4916-8550-33f4bfc1a857" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_3eb6d428-1fa4-4803-975a-f2e956ca2dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_us-gaap_ConstructionLoansMember_3eb6d428-1fa4-4803-975a-f2e956ca2dd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_f7c868f1-c584-470b-baf5-c40cf23777b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_us-gaap_ResidentialRealEstateMember_f7c868f1-c584-470b-baf5-c40cf23777b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_f41e63ac-23c7-4a2d-99f5-0dcb5507e537" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_f41e63ac-23c7-4a2d-99f5-0dcb5507e537" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_7aa1cb25-bad5-4c75-ac9c-408897d6c8bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_us-gaap_CommercialLoanMember_7aa1cb25-bad5-4c75-ac9c-408897d6c8bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MunicipalLoansMember_d49c9631-dda8-4780-92b3-70d36dc4ced8" xlink:href="sbsi-20230331.xsd#sbsi_MunicipalLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_sbsi_MunicipalLoansMember_d49c9631-dda8-4780-92b3-70d36dc4ced8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerLoanMember_92f24ad8-57c0-4dc6-9d0b-6d6910d37d0d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConsumerLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f0dc2f4b-d9fb-472c-b2fa-a98cc7173e7f" xlink:to="loc_us-gaap_ConsumerLoanMember_92f24ad8-57c0-4dc6-9d0b-6d6910d37d0d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_1f057ba2-9724-473f-b9a2-aa8673dbaa73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_9e6a749b-c9c8-451a-9dc4-7cf46c7c4816" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_1f057ba2-9724-473f-b9a2-aa8673dbaa73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_1f057ba2-9724-473f-b9a2-aa8673dbaa73_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_1f057ba2-9724-473f-b9a2-aa8673dbaa73" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_1f057ba2-9724-473f-b9a2-aa8673dbaa73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_1f057ba2-9724-473f-b9a2-aa8673dbaa73" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_82dc7e48-e35f-468f-8e18-5daa4004d2fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_82dc7e48-e35f-468f-8e18-5daa4004d2fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_fc8f8ad4-1f16-4580-a31f-371455469a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_fc8f8ad4-1f16-4580-a31f-371455469a4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_04d968d6-4a7d-4ff4-9b31-6c16752d3717" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_04d968d6-4a7d-4ff4-9b31-6c16752d3717" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_209a06c5-b0f6-4263-9b38-da8c82a963d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_209a06c5-b0f6-4263-9b38-da8c82a963d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetPastDueMember_d9634556-ba56-43f9-884f-e6afa98508c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialAssetPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_7098e54b-e262-4239-8807-37ff23ffe272" xlink:to="loc_us-gaap_FinancialAssetPastDueMember_d9634556-ba56-43f9-884f-e6afa98508c8" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesNonperformingAssetsbyAssetClassDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesNonperformingAssetsbyAssetClassDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesNonperformingAssetsbyAssetClassDetails" xlink:type="extended" id="iaefd48e6845d42399e97f794e83b832c_LoansandAllowanceforLoanLossesNonperformingAssetsbyAssetClassDetails">
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:href="sbsi-20230331.xsd#sbsi_NonperformingAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_7375c0c7-2e57-47e7-944d-a0b4a382ece9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_7375c0c7-2e57-47e7-944d-a0b4a382ece9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing_46bb0d47-c384-4059-b2b3-4e3319968ccb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing_46bb0d47-c384-4059-b2b3-4e3319968ccb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount_503a436a-80d3-4a50-a68f-aec6c95dcff3" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount_503a436a-80d3-4a50-a68f-aec6c95dcff3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateAcquiredThroughForeclosure_74f6fccb-0a3e-465c-8840-78289a35c787" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RealEstateAcquiredThroughForeclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_us-gaap_RealEstateAcquiredThroughForeclosure_74f6fccb-0a3e-465c-8840-78289a35c787" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherForeclosedAssets_480d8f1f-039d-4bf7-b741-0c13442c1526" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherForeclosedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_us-gaap_OtherForeclosedAssets_480d8f1f-039d-4bf7-b741-0c13442c1526" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableNonperformingAndRepossessedAssets_5d29dfed-caa9-41b8-b395-62d3116c8f44" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableNonperformingAndRepossessedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_sbsi_FinancingReceivableNonperformingAndRepossessedAssets_5d29dfed-caa9-41b8-b395-62d3116c8f44" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_NonperformingAssetsTable_5e04d0bd-d85f-47f3-92c7-69a1a2d78e71" xlink:href="sbsi-20230331.xsd#sbsi_NonperformingAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_sbsi_NonperformingAssetsLineItems_2603d4c5-27a2-410d-a198-1289183cd1cb" xlink:to="loc_sbsi_NonperformingAssetsTable_5e04d0bd-d85f-47f3-92c7-69a1a2d78e71" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentPerformanceStatusAxis_5748cc1e-840e-407a-ba4c-5288f6f031ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentPerformanceStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_NonperformingAssetsTable_5e04d0bd-d85f-47f3-92c7-69a1a2d78e71" xlink:to="loc_us-gaap_FinancialInstrumentPerformanceStatusAxis_5748cc1e-840e-407a-ba4c-5288f6f031ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentPerformanceStatusDomain_5748cc1e-840e-407a-ba4c-5288f6f031ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentPerformanceStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentPerformanceStatusAxis_5748cc1e-840e-407a-ba4c-5288f6f031ce" xlink:to="loc_us-gaap_FinancialInstrumentPerformanceStatusDomain_5748cc1e-840e-407a-ba4c-5288f6f031ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentPerformanceStatusDomain_44c59e5e-ba84-44f5-8d1b-79193d186273" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentPerformanceStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentPerformanceStatusAxis_5748cc1e-840e-407a-ba4c-5288f6f031ce" xlink:to="loc_us-gaap_FinancialInstrumentPerformanceStatusDomain_44c59e5e-ba84-44f5-8d1b-79193d186273" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonperformingFinancingReceivableMember_9795e673-aae6-4976-b060-f9a788500cc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonperformingFinancingReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentPerformanceStatusDomain_44c59e5e-ba84-44f5-8d1b-79193d186273" xlink:to="loc_us-gaap_NonperformingFinancingReceivableMember_9795e673-aae6-4976-b060-f9a788500cc5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_f73cb6aa-50f4-48e4-a812-cdab266a103f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_NonperformingAssetsTable_5e04d0bd-d85f-47f3-92c7-69a1a2d78e71" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_f73cb6aa-50f4-48e4-a812-cdab266a103f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f73cb6aa-50f4-48e4-a812-cdab266a103f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_f73cb6aa-50f4-48e4-a812-cdab266a103f" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_f73cb6aa-50f4-48e4-a812-cdab266a103f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_f73cb6aa-50f4-48e4-a812-cdab266a103f" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_dd81f485-aa58-4efc-9ff3-1e5a394817a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_us-gaap_ConstructionLoansMember_dd81f485-aa58-4efc-9ff3-1e5a394817a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_0b679a3f-350d-4986-aef6-c92e2c93719c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_us-gaap_ResidentialRealEstateMember_0b679a3f-350d-4986-aef6-c92e2c93719c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_a161fd47-b239-4d69-9342-07c7225ab134" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_a161fd47-b239-4d69-9342-07c7225ab134" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_fa51851e-5039-4017-a84a-cae7268c90c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_us-gaap_CommercialLoanMember_fa51851e-5039-4017-a84a-cae7268c90c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MunicipalLoansMember_4dec3a24-66f1-438f-a271-989ebf5b95b9" xlink:href="sbsi-20230331.xsd#sbsi_MunicipalLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_sbsi_MunicipalLoansMember_4dec3a24-66f1-438f-a271-989ebf5b95b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerLoanMember_c5dc3c12-6832-472a-8baf-e04dff0d204a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConsumerLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_us-gaap_ConsumerLoanMember_c5dc3c12-6832-472a-8baf-e04dff0d204a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DemandDepositOverdraftsMember_d29b7793-2657-4e59-abf1-cedf7547b6f3" xlink:href="sbsi-20230331.xsd#sbsi_DemandDepositOverdraftsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_c7e4138e-289d-4c35-91c0-4e41a51e3f58" xlink:to="loc_sbsi_DemandDepositOverdraftsMember_d29b7793-2657-4e59-abf1-cedf7547b6f3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_89ee2263-d747-4bd9-9c78-d26366967e84" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_NonperformingAssetsTable_5e04d0bd-d85f-47f3-92c7-69a1a2d78e71" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_89ee2263-d747-4bd9-9c78-d26366967e84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_89ee2263-d747-4bd9-9c78-d26366967e84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_89ee2263-d747-4bd9-9c78-d26366967e84" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_89ee2263-d747-4bd9-9c78-d26366967e84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_f4f76e17-16fd-454b-a645-2b4369600506" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_89ee2263-d747-4bd9-9c78-d26366967e84" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_f4f76e17-16fd-454b-a645-2b4369600506" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtendedMaturityMember_da1e5591-f3c5-4890-9e18-c158624d9eba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ExtendedMaturityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_f4f76e17-16fd-454b-a645-2b4369600506" xlink:to="loc_us-gaap_ExtendedMaturityMember_da1e5591-f3c5-4890-9e18-c158624d9eba" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesAllowanceforLoanLossesActivitybyPortfolioSegmentDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesAllowanceforLoanLossesActivitybyPortfolioSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesAllowanceforLoanLossesActivitybyPortfolioSegmentDetails" xlink:type="extended" id="ie0caa1ee7beb47b6a0db070d6ac45adb_LoansandAllowanceforLoanLossesAllowanceforLoanLossesActivitybyPortfolioSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_c8a4e6f5-1760-45f9-9741-7329ba37b359" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_c8a4e6f5-1760-45f9-9741-7329ba37b359" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_4d55eccd-4191-4ce6-8782-82049d86d04d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_4d55eccd-4191-4ce6-8782-82049d86d04d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_56cb5f63-a9f3-4c0a-af1f-ad196a43ea80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_56cb5f63-a9f3-4c0a-af1f-ad196a43ea80" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_11198e9e-f78f-4603-8a23-5c2102239979" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_11198e9e-f78f-4603-8a23-5c2102239979" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_c24558b9-bad8-48fe-b91b-11ea8df65d48" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_c24558b9-bad8-48fe-b91b-11ea8df65d48" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_1185f2ae-f631-4144-b2d5-e90d43afc792" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_9d91481f-2af0-4776-8ad8-77ba7c7f46cb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_1185f2ae-f631-4144-b2d5-e90d43afc792" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_78497e60-375e-40a0-b167-d2baf768325e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_4c3a977f-516d-4b3b-b1ca-84c0a68334ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_c8a4e6f5-1760-45f9-9741-7329ba37b359" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_4c3a977f-516d-4b3b-b1ca-84c0a68334ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_5342084b-3d03-4d51-b2f2-ab8ded15318b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_4c3a977f-516d-4b3b-b1ca-84c0a68334ac" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_5342084b-3d03-4d51-b2f2-ab8ded15318b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5342084b-3d03-4d51-b2f2-ab8ded15318b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_5342084b-3d03-4d51-b2f2-ab8ded15318b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5342084b-3d03-4d51-b2f2-ab8ded15318b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_5342084b-3d03-4d51-b2f2-ab8ded15318b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_4268910f-38e3-471d-9c49-cf9af97bba1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_us-gaap_ConstructionLoansMember_4268910f-38e3-471d-9c49-cf9af97bba1a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_306640cc-8ec3-439f-a16b-281d16246c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_us-gaap_ResidentialRealEstateMember_306640cc-8ec3-439f-a16b-281d16246c0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_1d4c101b-dd84-4432-bd49-887fd018923b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_1d4c101b-dd84-4432-bd49-887fd018923b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_9dc96f84-6604-4ff7-957a-241851213b4b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_us-gaap_CommercialLoanMember_9dc96f84-6604-4ff7-957a-241851213b4b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MunicipalLoansMember_ea6e89ea-f18b-4f84-80dd-81100280b93b" xlink:href="sbsi-20230331.xsd#sbsi_MunicipalLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_sbsi_MunicipalLoansMember_ea6e89ea-f18b-4f84-80dd-81100280b93b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerLoanMember_39f538ba-c857-45b4-8a4a-0bdbc2e77d68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConsumerLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_b90776da-4937-4138-bd16-d903bbf61326" xlink:to="loc_us-gaap_ConsumerLoanMember_39f538ba-c857-45b4-8a4a-0bdbc2e77d68" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LoansandAllowanceforLoanLossesNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LoansandAllowanceforLoanLossesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LoansandAllowanceforLoanLossesNarrativeDetails" xlink:type="extended" id="i50c1e498aa5b493eab3e0233aa8b9a35_LoansandAllowanceforLoanLossesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_GeneralLoanTerm_f3b063ca-c9d5-4827-a07e-f79539f57fb0" xlink:href="sbsi-20230331.xsd#sbsi_GeneralLoanTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_GeneralLoanTerm_f3b063ca-c9d5-4827-a07e-f79539f57fb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CommercialRealEstateOwnerandNonOwnerOccupiedRealEstate_a96e7959-c9d7-42c4-ad93-5f7fdf22c10c" xlink:href="sbsi-20230331.xsd#sbsi_CommercialRealEstateOwnerandNonOwnerOccupiedRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_CommercialRealEstateOwnerandNonOwnerOccupiedRealEstate_a96e7959-c9d7-42c4-ad93-5f7fdf22c10c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CommercialRealEstateMultifamily_9c89ac38-d901-4d89-b2f2-170cb55424ce" xlink:href="sbsi-20230331.xsd#sbsi_CommercialRealEstateMultifamily"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_CommercialRealEstateMultifamily_9c89ac38-d901-4d89-b2f2-170cb55424ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CommercialRealEstateFarmLand_c93d3a84-8ffc-4e09-b316-c5b331da1906" xlink:href="sbsi-20230331.xsd#sbsi_CommercialRealEstateFarmLand"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_CommercialRealEstateFarmLand_c93d3a84-8ffc-4e09-b316-c5b331da1906" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableNonaccrualInterestIncomeReversal_540353e4-b335-462b-940a-b139809ca125" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableNonaccrualInterestIncomeReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_FinancingReceivableNonaccrualInterestIncomeReversal_540353e4-b335-462b-940a-b139809ca125" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance_e406018e-6d19-4746-a1e5-53c88ae0b977" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance_e406018e-6d19-4746-a1e5-53c88ae0b977" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableCollateralDependent_b77a8750-3ff0-4b14-98e5-415c395ca70d" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableCollateralDependent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_FinancingReceivableCollateralDependent_b77a8750-3ff0-4b14-98e5-415c395ca70d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageLoansInProcessOfForeclosureAmount_bd206733-86c6-4437-b71f-fcae0581ce14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MortgageLoansInProcessOfForeclosureAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_us-gaap_MortgageLoansInProcessOfForeclosureAmount_bd206733-86c6-4437-b71f-fcae0581ce14" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodNumberOfLoansModified_f1fe59b4-2fbf-403c-a4c0-d6c60007c856" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodNumberOfLoansModified"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodNumberOfLoansModified_f1fe59b4-2fbf-403c-a4c0-d6c60007c856" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount_c18a7901-c17d-4fdd-a70a-4bcf540f82d2" xlink:href="sbsi-20230331.xsd#sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_sbsi_FinancingReceivableExcludingAccruedInterestModifiedInPeriodAmount_c18a7901-c17d-4fdd-a70a-4bcf540f82d2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivable_6b8023f1-2d43-43f9-821c-7736f7709816" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_us-gaap_InterestReceivable_6b8023f1-2d43-43f9-821c-7736f7709816" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_62ff98a5-1e64-4fdd-928a-782a9aeef160" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_62ff98a5-1e64-4fdd-928a-782a9aeef160" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_550dfb5e-f83c-4cf6-a558-21efb40c13aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_751b56a4-2143-49a8-83fe-da6562a63219" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_550dfb5e-f83c-4cf6-a558-21efb40c13aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_d996167d-e563-4715-a57b-9df105248658" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_550dfb5e-f83c-4cf6-a558-21efb40c13aa" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_d996167d-e563-4715-a57b-9df105248658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_d996167d-e563-4715-a57b-9df105248658_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_d996167d-e563-4715-a57b-9df105248658" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_d996167d-e563-4715-a57b-9df105248658_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_49320344-a8b2-4e48-bc73-9219e9e27c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_d996167d-e563-4715-a57b-9df105248658" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_49320344-a8b2-4e48-bc73-9219e9e27c6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_22d46a35-4472-44b4-af57-329f47be15e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_49320344-a8b2-4e48-bc73-9219e9e27c6a" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_22d46a35-4472-44b4-af57-329f47be15e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialLoanMember_ca495f4a-e00c-47d8-be30-cec3ebf1d13d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_49320344-a8b2-4e48-bc73-9219e9e27c6a" xlink:to="loc_us-gaap_CommercialLoanMember_ca495f4a-e00c-47d8-be30-cec3ebf1d13d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialRealEstateMember_65020890-c274-43ef-9137-7d40f8dd0922" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_49320344-a8b2-4e48-bc73-9219e9e27c6a" xlink:to="loc_us-gaap_ResidentialRealEstateMember_65020890-c274-43ef-9137-7d40f8dd0922" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_550dfb5e-f83c-4cf6-a558-21efb40c13aa" xlink:to="loc_srt_RangeAxis_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1" xlink:to="loc_srt_RangeMember_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5fc9498c-e2ca-440a-a5bc-ab03fcd6ad56" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_081cd815-3cd5-48ce-9fa7-fcb0b85d0fa1" xlink:to="loc_srt_RangeMember_5fc9498c-e2ca-440a-a5bc-ab03fcd6ad56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_fb46c654-769e-49c4-a7d2-814db6e55431" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5fc9498c-e2ca-440a-a5bc-ab03fcd6ad56" xlink:to="loc_srt_MinimumMember_fb46c654-769e-49c4-a7d2-814db6e55431" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0f36862b-4edd-4b50-ab4d-f7b0cf6ffc34" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5fc9498c-e2ca-440a-a5bc-ab03fcd6ad56" xlink:to="loc_srt_MaximumMember_0f36862b-4edd-4b50-ab4d-f7b0cf6ffc34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_550dfb5e-f83c-4cf6-a558-21efb40c13aa" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_6d959c98-2b32-4943-a2a2-44196dfb0aef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_d860f4a3-1f2e-4fe1-a6f0-9a731776dbf6" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_6d959c98-2b32-4943-a2a2-44196dfb0aef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtendedMaturityMember_519dd268-3a0c-49eb-8000-4883ab97f8ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ExtendedMaturityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_6d959c98-2b32-4943-a2a2-44196dfb0aef" xlink:to="loc_us-gaap_ExtendedMaturityMember_519dd268-3a0c-49eb-8000-4883ab97f8ea" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/BorrowingArrangementsDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#BorrowingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/BorrowingArrangementsDetails" xlink:type="extended" id="i7087031df69d40fa9ddd141c5e9a8fbb_BorrowingArrangementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_5ab4c86c-8f63-4eac-9659-cf7f6a751df1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_5ab4c86c-8f63-4eac-9659-cf7f6a751df1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch_4fb5b60b-47e3-409d-99e9-a6347d68dbc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch_4fb5b60b-47e3-409d-99e9-a6347d68dbc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowingsAverageAmountOutstanding_638908e6-6467-40f1-9a77-d1b1020bb974" xlink:href="sbsi-20230331.xsd#sbsi_BorrowingsAverageAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_sbsi_BorrowingsAverageAmountOutstanding_638908e6-6467-40f1-9a77-d1b1020bb974" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowingsMaximumMonthendOutstandingAmount_09332d3d-85b8-46c0-be57-156e505f26c3" xlink:href="sbsi-20230331.xsd#sbsi_BorrowingsMaximumMonthendOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_sbsi_BorrowingsMaximumMonthendOutstandingAmount_09332d3d-85b8-46c0-be57-156e505f26c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_5ef202b9-993c-4674-accf-4f6ab7825238" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_5ef202b9-993c-4674-accf-4f6ab7825238" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_15927508-b59c-4328-93ed-6900b4ef5fbe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_15927508-b59c-4328-93ed-6900b4ef5fbe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_83822489-2fa4-4927-8405-e21ca0ea8ae0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_83822489-2fa4-4927-8405-e21ca0ea8ae0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DebtTable_50c85f48-c1ad-4d48-8528-e574ad87391d" xlink:href="sbsi-20230331.xsd#sbsi_DebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1e7f5205-a3b6-467e-9645-7dbb54da6ce2" xlink:to="loc_sbsi_DebtTable_50c85f48-c1ad-4d48-8528-e574ad87391d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_feeaaa11-c782-4435-9e00-958c71517b98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_DebtTable_50c85f48-c1ad-4d48-8528-e574ad87391d" xlink:to="loc_us-gaap_DebtInstrumentAxis_feeaaa11-c782-4435-9e00-958c71517b98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_feeaaa11-c782-4435-9e00-958c71517b98_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_feeaaa11-c782-4435-9e00-958c71517b98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_feeaaa11-c782-4435-9e00-958c71517b98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_45380b8a-0dc4-462d-a62a-1bbbec286a14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_feeaaa11-c782-4435-9e00-958c71517b98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_45380b8a-0dc4-462d-a62a-1bbbec286a14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember_18d7fbf6-5e31-476a-800f-ae870d9857cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_45380b8a-0dc4-462d-a62a-1bbbec286a14" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember_18d7fbf6-5e31-476a-800f-ae870d9857cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_352e756a-54ec-4397-b177-f9eec2cf7d40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_45380b8a-0dc4-462d-a62a-1bbbec286a14" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_352e756a-54ec-4397-b177-f9eec2cf7d40" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/BorrowingsMaturitiesTableDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#BorrowingsMaturitiesTableDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/BorrowingsMaturitiesTableDetails" xlink:type="extended" id="i5e81fa4cbf304d428868a11f65198c08_BorrowingsMaturitiesTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInTheNextRollingTwelveMonths_23451c66-2434-406f-b6f3-dc1139550fc4" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInTheNextRollingTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInTheNextRollingTwelveMonths_23451c66-2434-406f-b6f3-dc1139550fc4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearTwo_caedc184-7a45-4427-adae-12611b614a52" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearTwo_caedc184-7a45-4427-adae-12611b614a52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearThree_14cb58a3-50c9-4821-b469-b870ae382878" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearThree_14cb58a3-50c9-4821-b469-b870ae382878" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFour_1f957471-a6dc-4bbd-a41f-420ec6e922ae" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFour_1f957471-a6dc-4bbd-a41f-420ec6e922ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFive_ba17304c-0dda-4591-9e34-35d4e4c1a6a0" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingYearFive_ba17304c-0dda-4591-9e34-35d4e4c1a6a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingAfterYearFive_6174e6cc-48d5-4ec5-8a3c-8b13e14155ae" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipalInRollingAfterYearFive_6174e6cc-48d5-4ec5-8a3c-8b13e14155ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipal_b454bb71-3d16-4380-969f-f80127afd67d" xlink:href="sbsi-20230331.xsd#sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_BorrowedFundsMaturitiesRepaymentsOfPrincipal_b454bb71-3d16-4380-969f-f80127afd67d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DebtTable_1df29baf-ce65-43b9-8f1e-865a36787705" xlink:href="sbsi-20230331.xsd#sbsi_DebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_cc09221c-0a7f-43c8-b56a-12b21b84c05d" xlink:to="loc_sbsi_DebtTable_1df29baf-ce65-43b9-8f1e-865a36787705" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sbsi_DebtTable_1df29baf-ce65-43b9-8f1e-865a36787705" xlink:to="loc_us-gaap_DebtInstrumentAxis_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a1cb65bc-d864-48c1-a8d5-123ca8039c55" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1e68d390-46c4-4150-81ed-e0c2e1bdf8aa" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a1cb65bc-d864-48c1-a8d5-123ca8039c55" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember_5b537876-c4a9-4c79-865a-765ea1ad91c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a1cb65bc-d864-48c1-a8d5-123ca8039c55" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseMember_5b537876-c4a9-4c79-865a-765ea1ad91c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_3f2ad8f4-16c1-42a0-86a1-03d87a8239a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a1cb65bc-d864-48c1-a8d5-123ca8039c55" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_3f2ad8f4-16c1-42a0-86a1-03d87a8239a6" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/BorrowingArrangementsNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#BorrowingArrangementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/BorrowingArrangementsNarrativeDetails" xlink:type="extended" id="i64bea03f99a146288b57ff44bb92b0de_BorrowingArrangementsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_LineOfCreditFacilityNumberOfCreditLinesMaintainedByCompany_a5484f7b-dcfa-411b-8650-31941c3295a3" xlink:href="sbsi-20230331.xsd#sbsi_LineOfCreditFacilityNumberOfCreditLinesMaintainedByCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_LineOfCreditFacilityNumberOfCreditLinesMaintainedByCompany_a5484f7b-dcfa-411b-8650-31941c3295a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_b7760225-1956-4ea8-b4c5-9949d0e0fb07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_b7760225-1956-4ea8-b4c5-9949d0e0fb07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_37ae0052-1bfd-4c60-b983-b0abae862361" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_37ae0052-1bfd-4c60-b983-b0abae862361" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchased_19a11c46-4ced-4f4f-9b7a-094a14c0f806" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalFundsPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_FederalFundsPurchased_19a11c46-4ced-4f4f-9b7a-094a14c0f806" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_LettersOfCreditFhlbAsCollateral_d993e631-0eda-4fd4-90fb-19f86f8eaa6b" xlink:href="sbsi-20230331.xsd#sbsi_LettersOfCreditFhlbAsCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_LettersOfCreditFhlbAsCollateral_d993e631-0eda-4fd4-90fb-19f86f8eaa6b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_RepurchaseAgreementCounterpartyMaturityofAgreements_d284c567-fe6d-4dc9-81d6-71d987f771a8" xlink:href="sbsi-20230331.xsd#sbsi_RepurchaseAgreementCounterpartyMaturityofAgreements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_RepurchaseAgreementCounterpartyMaturityofAgreements_d284c567-fe6d-4dc9-81d6-71d987f771a8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchase_15f52f9d-78ce-41cf-8e21-245926adc26d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchase_15f52f9d-78ce-41cf-8e21-245926adc26d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd_264f5b30-46c1-498d-80f1-35ad71df7ef5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd_264f5b30-46c1-498d-80f1-35ad71df7ef5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalHomeLoanBankAdvancesMaturitiesSummaryMaturityRange_bc298902-0dfb-4342-8874-9ce252f8b320" xlink:href="sbsi-20230331.xsd#sbsi_FederalHomeLoanBankAdvancesMaturitiesSummaryMaturityRange"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_FederalHomeLoanBankAdvancesMaturitiesSummaryMaturityRange_bc298902-0dfb-4342-8874-9ce252f8b320" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds_142bb7ef-c390-4ed0-a77f-1ba8ab5214d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds_142bb7ef-c390-4ed0-a77f-1ba8ab5214d9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_5bf5efb6-357a-4c37-aff0-5cd29600b7be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_5bf5efb6-357a-4c37-aff0-5cd29600b7be" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_AdditionalFundingAvailable_0748f6f8-1bc3-4452-8116-9424f9f64d2e" xlink:href="sbsi-20230331.xsd#sbsi_AdditionalFundingAvailable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_AdditionalFundingAvailable_0748f6f8-1bc3-4452-8116-9424f9f64d2e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_5de940d1-3c80-45c6-a5b4-2f7267ed5319" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_5de940d1-3c80-45c6-a5b4-2f7267ed5319" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_Numberofoutstandinglettersofcredit_178a8d47-9a51-4082-ab05-b395fc72c7a1" xlink:href="sbsi-20230331.xsd#sbsi_Numberofoutstandinglettersofcredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_sbsi_Numberofoutstandinglettersofcredit_178a8d47-9a51-4082-ab05-b395fc72c7a1" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_195e4ae3-014c-4360-ba49-e8f8c0409736" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_195e4ae3-014c-4360-ba49-e8f8c0409736" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_55a2d798-4fe5-437e-bc45-4d9ded65420f" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_b3bdfc38-f266-48b7-a906-521428d107c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_us-gaap_CreditFacilityAxis_b3bdfc38-f266-48b7-a906-521428d107c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_b3bdfc38-f266-48b7-a906-521428d107c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_b3bdfc38-f266-48b7-a906-521428d107c5" xlink:to="loc_us-gaap_CreditFacilityDomain_b3bdfc38-f266-48b7-a906-521428d107c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_1c1474f9-112b-4559-af71-3e84f7340f0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_b3bdfc38-f266-48b7-a906-521428d107c5" xlink:to="loc_us-gaap_CreditFacilityDomain_1c1474f9-112b-4559-af71-3e84f7340f0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalReserveDiscountWindowMember_bba4b28c-0aff-47a3-8839-8f88c41ef7e7" xlink:href="sbsi-20230331.xsd#sbsi_FederalReserveDiscountWindowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1c1474f9-112b-4559-af71-3e84f7340f0c" xlink:to="loc_sbsi_FederalReserveDiscountWindowMember_bba4b28c-0aff-47a3-8839-8f88c41ef7e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalReserveBankTermFundingProgramMember_5ff1c78c-ca13-4a65-9980-47639fcfccad" xlink:href="sbsi-20230331.xsd#sbsi_FederalReserveBankTermFundingProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1c1474f9-112b-4559-af71-3e84f7340f0c" xlink:to="loc_sbsi_FederalReserveBankTermFundingProgramMember_5ff1c78c-ca13-4a65-9980-47639fcfccad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d8cce1c6-a76d-4ade-8b69-b449b54fc95f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d8cce1c6-a76d-4ade-8b69-b449b54fc95f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_d8cce1c6-a76d-4ade-8b69-b449b54fc95f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d8cce1c6-a76d-4ade-8b69-b449b54fc95f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_d8cce1c6-a76d-4ade-8b69-b449b54fc95f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_621e5b3d-0899-4952-8d1c-ac0205c26129" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d8cce1c6-a76d-4ade-8b69-b449b54fc95f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_621e5b3d-0899-4952-8d1c-ac0205c26129" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_6c10b1f8-08ca-4ac8-92d6-133e40a67977" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_621e5b3d-0899-4952-8d1c-ac0205c26129" xlink:to="loc_us-gaap_CashFlowHedgingMember_6c10b1f8-08ca-4ac8-92d6-133e40a67977" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_43b6c0af-b9ca-4994-95a3-c4aacb8060aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_43b6c0af-b9ca-4994-95a3-c4aacb8060aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_43b6c0af-b9ca-4994-95a3-c4aacb8060aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_43b6c0af-b9ca-4994-95a3-c4aacb8060aa" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_43b6c0af-b9ca-4994-95a3-c4aacb8060aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d68865d3-94e3-444d-a51e-a79a6d2d1cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_43b6c0af-b9ca-4994-95a3-c4aacb8060aa" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d68865d3-94e3-444d-a51e-a79a6d2d1cb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_be47fcb1-5243-41d7-929a-29c3219ce79a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d68865d3-94e3-444d-a51e-a79a6d2d1cb7" xlink:to="loc_us-gaap_InterestRateSwapMember_be47fcb1-5243-41d7-929a-29c3219ce79a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_2183c58f-45b5-4421-83d6-81719de20236" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_us-gaap_VariableRateAxis_2183c58f-45b5-4421-83d6-81719de20236" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_2183c58f-45b5-4421-83d6-81719de20236_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_2183c58f-45b5-4421-83d6-81719de20236" xlink:to="loc_us-gaap_VariableRateDomain_2183c58f-45b5-4421-83d6-81719de20236_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_0fb535ac-7017-4e00-b135-ac8255bfdef8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_2183c58f-45b5-4421-83d6-81719de20236" xlink:to="loc_us-gaap_VariableRateDomain_0fb535ac-7017-4e00-b135-ac8255bfdef8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember_1cf3358e-423a-43ff-9752-16b925da63a9" xlink:href="sbsi-20230331.xsd#sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_0fb535ac-7017-4e00-b135-ac8255bfdef8" xlink:to="loc_sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember_1cf3358e-423a-43ff-9752-16b925da63a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_238fe5de-9eff-4335-a584-34297cebd1f0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_srt_RangeAxis_238fe5de-9eff-4335-a584-34297cebd1f0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_238fe5de-9eff-4335-a584-34297cebd1f0_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_238fe5de-9eff-4335-a584-34297cebd1f0" xlink:to="loc_srt_RangeMember_238fe5de-9eff-4335-a584-34297cebd1f0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_721c6665-f076-4a92-b7e0-d95a44eda974" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_238fe5de-9eff-4335-a584-34297cebd1f0" xlink:to="loc_srt_RangeMember_721c6665-f076-4a92-b7e0-d95a44eda974" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_78bf337a-0875-42ad-99a7-3d5842e672e6" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_721c6665-f076-4a92-b7e0-d95a44eda974" xlink:to="loc_srt_MinimumMember_78bf337a-0875-42ad-99a7-3d5842e672e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2fa7c310-9752-40ed-a9cb-20c9a0c8c5f2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_721c6665-f076-4a92-b7e0-d95a44eda974" xlink:to="loc_srt_MaximumMember_2fa7c310-9752-40ed-a9cb-20c9a0c8c5f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_306aa98d-ca25-4cb1-bc04-c334f358162c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_1ee6879b-4fa8-4a2d-b7da-b15f4b3b5a1b" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_306aa98d-ca25-4cb1-bc04-c334f358162c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_306aa98d-ca25-4cb1-bc04-c334f358162c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_306aa98d-ca25-4cb1-bc04-c334f358162c" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_306aa98d-ca25-4cb1-bc04-c334f358162c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_306aa98d-ca25-4cb1-bc04-c334f358162c" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FrostBankMember_5c821878-5db7-4ea5-9d26-9ae8b01cbfcd" xlink:href="sbsi-20230331.xsd#sbsi_FrostBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:to="loc_sbsi_FrostBankMember_5c821878-5db7-4ea5-9d26-9ae8b01cbfcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_TibIndependentBankersBankMember_164e50f4-1b26-42fa-bfb4-35cdb675aa81" xlink:href="sbsi-20230331.xsd#sbsi_TibIndependentBankersBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:to="loc_sbsi_TibIndependentBankersBankMember_164e50f4-1b26-42fa-bfb4-35cdb675aa81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ComericaBankMember_5e97d583-f583-4362-b14e-01ac55937bd9" xlink:href="sbsi-20230331.xsd#sbsi_ComericaBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:to="loc_sbsi_ComericaBankMember_5e97d583-f583-4362-b14e-01ac55937bd9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalReserveDiscountWindowMember_7b94ef10-bf8f-4037-aca4-0f45127862fa" xlink:href="sbsi-20230331.xsd#sbsi_FederalReserveDiscountWindowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:to="loc_sbsi_FederalReserveDiscountWindowMember_7b94ef10-bf8f-4037-aca4-0f45127862fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FederalReserveBankTermFundingProgramMember_7fed08f7-9715-4a96-a68d-7666412de4dc" xlink:href="sbsi-20230331.xsd#sbsi_FederalReserveBankTermFundingProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_cdb3da63-d825-4533-94a8-4931ba331733" xlink:to="loc_sbsi_FederalReserveBankTermFundingProgramMember_7fed08f7-9715-4a96-a68d-7666412de4dc" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LongtermDebtOtherLongtermDebtDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LongtermDebtOtherLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LongtermDebtOtherLongtermDebtDetails" xlink:type="extended" id="iea24f55f9b5c4bd8a147c27e0dfc52cb_LongtermDebtOtherLongtermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentsAbstract_9d7aab9a-f081-4ef9-9278-f07beae38d0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_us-gaap_DebtInstrumentsAbstract_9d7aab9a-f081-4ef9-9278-f07beae38d0c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebt_0923d648-4538-4051-b4b8-4769849552fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubordinatedDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentsAbstract_9d7aab9a-f081-4ef9-9278-f07beae38d0c" xlink:to="loc_us-gaap_SubordinatedDebt_0923d648-4538-4051-b4b8-4769849552fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermDebt_d40610bf-aebf-43ff-940b-bdcd23f531a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentsAbstract_9d7aab9a-f081-4ef9-9278-f07beae38d0c" xlink:to="loc_us-gaap_OtherLongTermDebt_d40610bf-aebf-43ff-940b-bdcd23f531a5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_71bbbf0c-ba67-4a59-b12b-74f16e7c5aaa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentsAbstract_9d7aab9a-f081-4ef9-9278-f07beae38d0c" xlink:to="loc_us-gaap_LongTermDebt_71bbbf0c-ba67-4a59-b12b-74f16e7c5aaa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_f734bbcd-39dd-4a93-b21d-aa5c38e3cf7f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_f734bbcd-39dd-4a93-b21d-aa5c38e3cf7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_4bb4532c-6c91-4941-a40d-c2df424876ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_4bb4532c-6c91-4941-a40d-c2df424876ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SubordinatedNotesRemainingMaturity_ebec2a45-538c-41a9-a8f5-28d1f397b8be" xlink:href="sbsi-20230331.xsd#sbsi_SubordinatedNotesRemainingMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_sbsi_SubordinatedNotesRemainingMaturity_ebec2a45-538c-41a9-a8f5-28d1f397b8be" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_a7b3f731-a259-4681-9fb8-a60232ede976" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_a7b3f731-a259-4681-9fb8-a60232ede976" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_da17cd10-f1b5-4a24-80de-d5a2868e6e9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9acda0ee-68bb-4935-9143-73e81d90b648" xlink:to="loc_us-gaap_DebtInstrumentTable_da17cd10-f1b5-4a24-80de-d5a2868e6e9c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_7cdb7df3-6722-4928-89c4-6e99571a93bf" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_da17cd10-f1b5-4a24-80de-d5a2868e6e9c" xlink:to="loc_srt_RangeAxis_7cdb7df3-6722-4928-89c4-6e99571a93bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7cdb7df3-6722-4928-89c4-6e99571a93bf_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_7cdb7df3-6722-4928-89c4-6e99571a93bf" xlink:to="loc_srt_RangeMember_7cdb7df3-6722-4928-89c4-6e99571a93bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_94e6302b-3e12-4e72-bf54-806a6e2d0016" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_7cdb7df3-6722-4928-89c4-6e99571a93bf" xlink:to="loc_srt_RangeMember_94e6302b-3e12-4e72-bf54-806a6e2d0016" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_844cc3d2-ea15-45ce-80ca-c3043b340ede" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_94e6302b-3e12-4e72-bf54-806a6e2d0016" xlink:to="loc_srt_MinimumMember_844cc3d2-ea15-45ce-80ca-c3043b340ede" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_f70b0fc7-1261-4b28-a031-439044ed26b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_da17cd10-f1b5-4a24-80de-d5a2868e6e9c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_f70b0fc7-1261-4b28-a031-439044ed26b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f70b0fc7-1261-4b28-a031-439044ed26b3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f70b0fc7-1261-4b28-a031-439044ed26b3" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f70b0fc7-1261-4b28-a031-439044ed26b3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f70b0fc7-1261-4b28-a031-439044ed26b3" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember_c14305f3-cf4e-4acc-a311-fa1f3828ace7" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:to="loc_sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember_c14305f3-cf4e-4acc-a311-fa1f3828ace7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustIvMember_bb2cb608-44ca-41d2-9e5f-21cf818cc26a" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustIvMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:to="loc_sbsi_SouthsideStatutoryTrustIvMember_bb2cb608-44ca-41d2-9e5f-21cf818cc26a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustVMember_0f83f93b-5b40-4d78-a609-8ec7a6189e08" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:to="loc_sbsi_SouthsideStatutoryTrustVMember_0f83f93b-5b40-4d78-a609-8ec7a6189e08" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MagnoliaTrustCompanyIMember_abd092fd-a563-4f46-a526-29b4db5302e5" xlink:href="sbsi-20230331.xsd#sbsi_MagnoliaTrustCompanyIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:to="loc_sbsi_MagnoliaTrustCompanyIMember_abd092fd-a563-4f46-a526-29b4db5302e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_A3875SubordinatedNotesMember_424ea4d2-1029-41ca-b79b-614a2b3e648f" xlink:href="sbsi-20230331.xsd#sbsi_A3875SubordinatedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_93124070-ad3f-432b-b1c3-98ea2a32aa77" xlink:to="loc_sbsi_A3875SubordinatedNotesMember_424ea4d2-1029-41ca-b79b-614a2b3e648f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/LongtermDebtLTDebtInterestRatesDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#LongtermDebtLTDebtInterestRatesDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/LongtermDebtLTDebtInterestRatesDetails" xlink:type="extended" id="i5a212f3a4349449782be17669d72ccd5_LongtermDebtLTDebtInterestRatesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_d4e71afb-a824-4d0a-8891-dd6540fa6d37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_d4e71afb-a824-4d0a-8891-dd6540fa6d37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermDebt_3193714e-afb5-4b70-9419-1dcde3763416" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:to="loc_us-gaap_OtherLongTermDebt_3193714e-afb5-4b70-9419-1dcde3763416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_30477f02-474e-45b2-b5e3-3b2ab70378c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_30477f02-474e-45b2-b5e3-3b2ab70378c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_d67a9e88-eb4e-4660-b658-971e3cf15101" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_d67a9e88-eb4e-4660-b658-971e3cf15101" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_1a61fd94-8050-4d31-b0b9-398154444d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19156007-6d6c-48a8-906e-87edc458bbec" xlink:to="loc_us-gaap_DebtInstrumentTable_1a61fd94-8050-4d31-b0b9-398154444d7a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_19178d48-fb57-4e54-8c14-2641b8300df4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a61fd94-8050-4d31-b0b9-398154444d7a" xlink:to="loc_srt_StatementScenarioAxis_19178d48-fb57-4e54-8c14-2641b8300df4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_19178d48-fb57-4e54-8c14-2641b8300df4_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_19178d48-fb57-4e54-8c14-2641b8300df4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_19178d48-fb57-4e54-8c14-2641b8300df4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_c360bb58-2a59-4d2e-a331-6216e550277a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_19178d48-fb57-4e54-8c14-2641b8300df4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_c360bb58-2a59-4d2e-a331-6216e550277a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_063f5d27-e6be-47ff-ad61-66e880c2bc95" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_c360bb58-2a59-4d2e-a331-6216e550277a" xlink:to="loc_srt_ScenarioForecastMember_063f5d27-e6be-47ff-ad61-66e880c2bc95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_39623454-3969-4fd2-9ded-5c3308890ee5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a61fd94-8050-4d31-b0b9-398154444d7a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_39623454-3969-4fd2-9ded-5c3308890ee5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_39623454-3969-4fd2-9ded-5c3308890ee5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_39623454-3969-4fd2-9ded-5c3308890ee5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_39623454-3969-4fd2-9ded-5c3308890ee5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_39623454-3969-4fd2-9ded-5c3308890ee5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember_0557b36d-d041-4b07-9001-ebca7ce1b63f" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:to="loc_sbsi_SouthsideStatutoryTrustIIInetofunamortizeddebtissuancecostsMember_0557b36d-d041-4b07-9001-ebca7ce1b63f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustIvMember_679c6dd3-6b57-4631-ae5b-807cce01e227" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustIvMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:to="loc_sbsi_SouthsideStatutoryTrustIvMember_679c6dd3-6b57-4631-ae5b-807cce01e227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_SouthsideStatutoryTrustVMember_8d39bff6-9cfe-4075-b111-40c9e42c074d" xlink:href="sbsi-20230331.xsd#sbsi_SouthsideStatutoryTrustVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:to="loc_sbsi_SouthsideStatutoryTrustVMember_8d39bff6-9cfe-4075-b111-40c9e42c074d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MagnoliaTrustCompanyIMember_917906e6-f7ed-4f95-8aa8-a1f6822a029c" xlink:href="sbsi-20230331.xsd#sbsi_MagnoliaTrustCompanyIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:to="loc_sbsi_MagnoliaTrustCompanyIMember_917906e6-f7ed-4f95-8aa8-a1f6822a029c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_A3875SubordinatedNotesMember_6bafcc5b-135c-4866-8a2e-c6d6b7eeac4b" xlink:href="sbsi-20230331.xsd#sbsi_A3875SubordinatedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c8753ddc-5baf-45ab-abd7-b8aeb7c8ca35" xlink:to="loc_sbsi_A3875SubordinatedNotesMember_6bafcc5b-135c-4866-8a2e-c6d6b7eeac4b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_86623af9-dea5-4af0-bae5-ce887fdcf5e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a61fd94-8050-4d31-b0b9-398154444d7a" xlink:to="loc_us-gaap_VariableRateAxis_86623af9-dea5-4af0-bae5-ce887fdcf5e2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_86623af9-dea5-4af0-bae5-ce887fdcf5e2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_86623af9-dea5-4af0-bae5-ce887fdcf5e2" xlink:to="loc_us-gaap_VariableRateDomain_86623af9-dea5-4af0-bae5-ce887fdcf5e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_b9739a04-ccfc-4859-be7e-3a012a28a63e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_86623af9-dea5-4af0-bae5-ce887fdcf5e2" xlink:to="loc_us-gaap_VariableRateDomain_b9739a04-ccfc-4859-be7e-3a012a28a63e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember_97d314d4-632e-411e-84d8-0a4d6e65c34f" xlink:href="sbsi-20230331.xsd#sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_b9739a04-ccfc-4859-be7e-3a012a28a63e" xlink:to="loc_sbsi_ThreeMonthLondonInterbankOfferedRateLIBORMember_97d314d4-632e-411e-84d8-0a4d6e65c34f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_07f86754-da07-4be8-8a10-7669b0ff58fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_b9739a04-ccfc-4859-be7e-3a012a28a63e" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_07f86754-da07-4be8-8a10-7669b0ff58fd" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/EmployeeBenefitPlansDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#EmployeeBenefitPlansDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/EmployeeBenefitPlansDetails" xlink:type="extended" id="ie361417392374e559d0a42105ef401b6_EmployeeBenefitPlansDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_7e5b70db-c07d-4b5f-97af-8236dc02992b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_7e5b70db-c07d-4b5f-97af-8236dc02992b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_0fd70f87-0964-4b55-9d6d-768a7c933fbc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_0fd70f87-0964-4b55-9d6d-768a7c933fbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_e49b1421-505e-411b-aa02-d7617b03e77e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_e49b1421-505e-411b-aa02-d7617b03e77e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_eb201339-a9dc-4239-888e-a9e9847e189f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_eb201339-a9dc-4239-888e-a9e9847e189f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_b2a3f8e9-ee0c-4366-b29d-c197794b5154" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_960ed43f-acfd-46b6-94f5-774262f0e4fb" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_b2a3f8e9-ee0c-4366-b29d-c197794b5154" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_b2a3f8e9-ee0c-4366-b29d-c197794b5154" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_9a067955-4e3d-4dc2-a63a-88f1e575f99c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_6da3aa3f-9e37-4ae7-99b6-2154130fcaeb" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_9a067955-4e3d-4dc2-a63a-88f1e575f99c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_13cfebc1-c283-4763-b882-082eec89d628" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_9a067955-4e3d-4dc2-a63a-88f1e575f99c" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_13cfebc1-c283-4763-b882-082eec89d628" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_a6518a11-a890-45b1-ae42-45a65299e5ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_9a067955-4e3d-4dc2-a63a-88f1e575f99c" xlink:to="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_a6518a11-a890-45b1-ae42-45a65299e5ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember_f8c48346-44ca-419f-b97e-ef95bd2fc013" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_9a067955-4e3d-4dc2-a63a-88f1e575f99c" xlink:to="loc_us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember_f8c48346-44ca-419f-b97e-ef95bd2fc013" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/EmployeeBenefitPlansNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#EmployeeBenefitPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/EmployeeBenefitPlansNarrativeDetails" xlink:type="extended" id="i176d97e45770491799aa01be4e1e9a34_EmployeeBenefitPlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_ece83dfa-a504-4521-9b61-9ead6b51eceb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_AdjustmentToPensionLiability_ff41b18c-b8e4-464c-9d07-53e588347c01" xlink:href="sbsi-20230331.xsd#sbsi_AdjustmentToPensionLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_ece83dfa-a504-4521-9b61-9ead6b51eceb" xlink:to="loc_sbsi_AdjustmentToPensionLiability_ff41b18c-b8e4-464c-9d07-53e588347c01" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef8b26e0-a2d8-4bad-8df1-d7e5537d4b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_ece83dfa-a504-4521-9b61-9ead6b51eceb" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef8b26e0-a2d8-4bad-8df1-d7e5537d4b9d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_ef8b26e0-a2d8-4bad-8df1-d7e5537d4b9d" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_285f9bc1-c391-46e2-8f55-009a5bc5a993" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_a01127dc-c6a6-482a-ae7b-f3fe1e04a43d" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_285f9bc1-c391-46e2-8f55-009a5bc5a993" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_baa6a6d5-b8d5-4192-a975-7311a422c125" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_285f9bc1-c391-46e2-8f55-009a5bc5a993" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_baa6a6d5-b8d5-4192-a975-7311a422c125" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_bb1c0764-75c3-4fa0-9375-46227b517c0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_285f9bc1-c391-46e2-8f55-009a5bc5a993" xlink:to="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_bb1c0764-75c3-4fa0-9375-46227b517c0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember_06276b8e-3ac5-4cec-b1cd-ee08699af571" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_285f9bc1-c391-46e2-8f55-009a5bc5a993" xlink:to="loc_us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember_06276b8e-3ac5-4cec-b1cd-ee08699af571" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesScheduleOfDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#DerivativeFinancialInstrumentsandHedgingActivitiesScheduleOfDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesScheduleOfDerivativeInstrumentsDetails" xlink:type="extended" id="ibffcbc69783f4e6ca3f862bdd1de3e68_DerivativeFinancialInstrumentsandHedgingActivitiesScheduleOfDerivativeInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueConcentrationOfRiskDerivativeFinancialInstrumentsAssets_491c72e3-0fa0-46d6-a213-a7499c26886e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueConcentrationOfRiskDerivativeFinancialInstrumentsAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:to="loc_us-gaap_FairValueConcentrationOfRiskDerivativeFinancialInstrumentsAssets_491c72e3-0fa0-46d6-a213-a7499c26886e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_0cf47b37-bd77-45b8-ad8e-31eb485931f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:to="loc_us-gaap_DerivativeNotionalAmount_0cf47b37-bd77-45b8-ad8e-31eb485931f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:to="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_93639b8c-dac0-4752-b8af-ca52ba554ad8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_93639b8c-dac0-4752-b8af-ca52ba554ad8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiability_b1cfdfa1-2d98-421c-80a7-3f320df7b04b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssetFairValueGrossLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossLiability_b1cfdfa1-2d98-421c-80a7-3f320df7b04b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_254e0039-7dea-4d32-b1a0-1b446ce86b11" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:to="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_254e0039-7dea-4d32-b1a0-1b446ce86b11" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_429f30b1-373a-4ace-8b9c-0d3316f3bdc7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_4f12f5ca-78ef-471f-9566-05f79e13cb6f" xlink:to="loc_us-gaap_DerivativeAssets_429f30b1-373a-4ace-8b9c-0d3316f3bdc7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:to="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_8bf00242-36c9-4cfa-9995-ab974c95da89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_8bf00242-36c9-4cfa-9995-ab974c95da89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_9717e8b0-a4ce-4897-81fa-4b2b3d18f358" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_9717e8b0-a4ce-4897-81fa-4b2b3d18f358" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_005f6d48-0f42-42ab-af3a-7a574af02768" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:to="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_005f6d48-0f42-42ab-af3a-7a574af02768" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_b37fa814-c54a-435e-8929-f389a194ada6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLiabilitiesAbstract_f6d0ab1a-0e22-4be3-943d-15db9e92d798" xlink:to="loc_us-gaap_DerivativeLiabilities_b37fa814-c54a-435e-8929-f389a194ada6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_9ff9fff4-3a3d-478e-852a-ca966d2a97d5" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_e752f855-6e1f-447e-b558-0f6775b62c1e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:to="loc_srt_CounterpartyNameAxis_e752f855-6e1f-447e-b558-0f6775b62c1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e752f855-6e1f-447e-b558-0f6775b62c1e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_e752f855-6e1f-447e-b558-0f6775b62c1e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e752f855-6e1f-447e-b558-0f6775b62c1e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6703845d-d862-47f2-9651-04a05d9b58f4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_e752f855-6e1f-447e-b558-0f6775b62c1e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6703845d-d862-47f2-9651-04a05d9b58f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancialInstitutionCounterpartiesMember_c2853819-8fb3-419b-8374-8631d0967846" xlink:href="sbsi-20230331.xsd#sbsi_FinancialInstitutionCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6703845d-d862-47f2-9651-04a05d9b58f4" xlink:to="loc_sbsi_FinancialInstitutionCounterpartiesMember_c2853819-8fb3-419b-8374-8631d0967846" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CustomerCounterpartiesMember_a1fbc9ed-0fc0-4b48-abfc-611a2b4e4e6f" xlink:href="sbsi-20230331.xsd#sbsi_CustomerCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6703845d-d862-47f2-9651-04a05d9b58f4" xlink:to="loc_sbsi_CustomerCounterpartiesMember_a1fbc9ed-0fc0-4b48-abfc-611a2b4e4e6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_0908e575-3b3a-416f-b8d2-079b87e252c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:to="loc_us-gaap_HedgingDesignationAxis_0908e575-3b3a-416f-b8d2-079b87e252c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_0908e575-3b3a-416f-b8d2-079b87e252c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_0908e575-3b3a-416f-b8d2-079b87e252c5" xlink:to="loc_us-gaap_HedgingDesignationDomain_0908e575-3b3a-416f-b8d2-079b87e252c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a00ffdf5-0659-447e-91ae-5c34604f00fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_0908e575-3b3a-416f-b8d2-079b87e252c5" xlink:to="loc_us-gaap_HedgingDesignationDomain_a00ffdf5-0659-447e-91ae-5c34604f00fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f898d303-d139-44db-9ffd-fde94216745c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_a00ffdf5-0659-447e-91ae-5c34604f00fe" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f898d303-d139-44db-9ffd-fde94216745c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_39c4abf2-8906-4075-8f04-1deb14e895ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_a00ffdf5-0659-447e-91ae-5c34604f00fe" xlink:to="loc_us-gaap_NondesignatedMember_39c4abf2-8906-4075-8f04-1deb14e895ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_15dee5f4-d77a-481b-92db-94895d04229d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_15dee5f4-d77a-481b-92db-94895d04229d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_15dee5f4-d77a-481b-92db-94895d04229d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_15dee5f4-d77a-481b-92db-94895d04229d" xlink:to="loc_us-gaap_HedgingRelationshipDomain_15dee5f4-d77a-481b-92db-94895d04229d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_2b25f140-986e-43b1-a11a-753e775987ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_15dee5f4-d77a-481b-92db-94895d04229d" xlink:to="loc_us-gaap_HedgingRelationshipDomain_2b25f140-986e-43b1-a11a-753e775987ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_764e3c67-ea58-46ec-938c-daafdd4b7c6c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_2b25f140-986e-43b1-a11a-753e775987ff" xlink:to="loc_us-gaap_CashFlowHedgingMember_764e3c67-ea58-46ec-938c-daafdd4b7c6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_dbf1fd23-bf41-482b-8033-2fd8974446bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_2b25f140-986e-43b1-a11a-753e775987ff" xlink:to="loc_us-gaap_FairValueHedgingMember_dbf1fd23-bf41-482b-8033-2fd8974446bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_023c8441-77c0-4417-bafe-84467539bb77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_b922c61a-046f-4563-b18d-f1418e79352e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_023c8441-77c0-4417-bafe-84467539bb77" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_023c8441-77c0-4417-bafe-84467539bb77_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_023c8441-77c0-4417-bafe-84467539bb77" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_023c8441-77c0-4417-bafe-84467539bb77_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c0ee1161-b1fd-4ba6-aaf6-d11f499eadcc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_023c8441-77c0-4417-bafe-84467539bb77" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c0ee1161-b1fd-4ba6-aaf6-d11f499eadcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_3afa7111-9116-4d03-9fc2-62545505bbfe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_c0ee1161-b1fd-4ba6-aaf6-d11f499eadcc" xlink:to="loc_us-gaap_InterestRateSwapMember_3afa7111-9116-4d03-9fc2-62545505bbfe" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesWeightedAverageRemainingMaturityLivesandRatesofInterestRateSwapsDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#DerivativeFinancialInstrumentsandHedgingActivitiesWeightedAverageRemainingMaturityLivesandRatesofInterestRateSwapsDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesWeightedAverageRemainingMaturityLivesandRatesofInterestRateSwapsDetails" xlink:type="extended" id="i37449bbde1934971991c51080328b2a6_DerivativeFinancialInstrumentsandHedgingActivitiesWeightedAverageRemainingMaturityLivesandRatesofInterestRateSwapsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_c1adea40-9124-45a9-8056-ce8149fe1f92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:to="loc_us-gaap_DerivativeNotionalAmount_c1adea40-9124-45a9-8056-ce8149fe1f92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageRemainingMaturity1_2a9811c9-4f07-4765-bc74-c27f86f144f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAverageRemainingMaturity1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:to="loc_us-gaap_DerivativeAverageRemainingMaturity1_2a9811c9-4f07-4765-bc74-c27f86f144f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DerivativeWeightedAverageReceiveRate_a739a5c4-0f59-4ee6-96d6-fad4b1d97887" xlink:href="sbsi-20230331.xsd#sbsi_DerivativeWeightedAverageReceiveRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:to="loc_sbsi_DerivativeWeightedAverageReceiveRate_a739a5c4-0f59-4ee6-96d6-fad4b1d97887" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_DerivativeWeightedAveragePayRate_4ffce0f5-b030-4621-8085-89c6b4a211be" xlink:href="sbsi-20230331.xsd#sbsi_DerivativeWeightedAveragePayRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:to="loc_sbsi_DerivativeWeightedAveragePayRate_4ffce0f5-b030-4621-8085-89c6b4a211be" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_ef6a1cfe-c633-4bba-8cf7-95429ff2cda7" xlink:to="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_6935e44a-50a4-4130-8315-cde9498bb0e1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:to="loc_srt_CounterpartyNameAxis_6935e44a-50a4-4130-8315-cde9498bb0e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6935e44a-50a4-4130-8315-cde9498bb0e1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_6935e44a-50a4-4130-8315-cde9498bb0e1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6935e44a-50a4-4130-8315-cde9498bb0e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b2dc6b47-c764-4457-979f-a7c8b419ef30" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_6935e44a-50a4-4130-8315-cde9498bb0e1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b2dc6b47-c764-4457-979f-a7c8b419ef30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_FinancialInstitutionCounterpartiesMember_b3390511-782a-450f-a0d1-99d3c2748d90" xlink:href="sbsi-20230331.xsd#sbsi_FinancialInstitutionCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b2dc6b47-c764-4457-979f-a7c8b419ef30" xlink:to="loc_sbsi_FinancialInstitutionCounterpartiesMember_b3390511-782a-450f-a0d1-99d3c2748d90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CustomerCounterpartiesMember_af291632-eaba-4d61-b4c0-5791e8827075" xlink:href="sbsi-20230331.xsd#sbsi_CustomerCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b2dc6b47-c764-4457-979f-a7c8b419ef30" xlink:to="loc_sbsi_CustomerCounterpartiesMember_af291632-eaba-4d61-b4c0-5791e8827075" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_542caffa-b2c8-483a-9c7c-02abfd2d6463" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_542caffa-b2c8-483a-9c7c-02abfd2d6463" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_542caffa-b2c8-483a-9c7c-02abfd2d6463_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_542caffa-b2c8-483a-9c7c-02abfd2d6463" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_542caffa-b2c8-483a-9c7c-02abfd2d6463_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_08213f46-7f7c-4c89-864e-85931a8e9983" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_542caffa-b2c8-483a-9c7c-02abfd2d6463" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_08213f46-7f7c-4c89-864e-85931a8e9983" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_93296b24-5e5f-46b7-841c-793a13cc2bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08213f46-7f7c-4c89-864e-85931a8e9983" xlink:to="loc_us-gaap_InterestRateSwapMember_93296b24-5e5f-46b7-841c-793a13cc2bc8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b4c5e212-462a-4676-9331-7e2efff75271" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b4c5e212-462a-4676-9331-7e2efff75271" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_b4c5e212-462a-4676-9331-7e2efff75271_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b4c5e212-462a-4676-9331-7e2efff75271" xlink:to="loc_us-gaap_HedgingRelationshipDomain_b4c5e212-462a-4676-9331-7e2efff75271_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_5fa5438c-1022-4ccb-b587-d6104c10214f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b4c5e212-462a-4676-9331-7e2efff75271" xlink:to="loc_us-gaap_HedgingRelationshipDomain_5fa5438c-1022-4ccb-b587-d6104c10214f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_26e5a1bd-d995-4653-ad4c-db7d18a18104" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_5fa5438c-1022-4ccb-b587-d6104c10214f" xlink:to="loc_us-gaap_CashFlowHedgingMember_26e5a1bd-d995-4653-ad4c-db7d18a18104" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_ddb90637-2abc-4c7d-847b-5de0c09c6e64" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_5fa5438c-1022-4ccb-b587-d6104c10214f" xlink:to="loc_us-gaap_FairValueHedgingMember_ddb90637-2abc-4c7d-847b-5de0c09c6e64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_99dddee6-5ce8-442c-8a8b-b1182213ff1f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_0bbf9689-952d-4f64-b869-8bc98c7d7015" xlink:to="loc_us-gaap_HedgingDesignationAxis_99dddee6-5ce8-442c-8a8b-b1182213ff1f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_99dddee6-5ce8-442c-8a8b-b1182213ff1f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_99dddee6-5ce8-442c-8a8b-b1182213ff1f" xlink:to="loc_us-gaap_HedgingDesignationDomain_99dddee6-5ce8-442c-8a8b-b1182213ff1f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_b2f56a62-027b-475a-9793-d7268bdd5441" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_99dddee6-5ce8-442c-8a8b-b1182213ff1f" xlink:to="loc_us-gaap_HedgingDesignationDomain_b2f56a62-027b-475a-9793-d7268bdd5441" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f3f29b86-a1bc-4bc2-99cd-e48a924434f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_b2f56a62-027b-475a-9793-d7268bdd5441" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f3f29b86-a1bc-4bc2-99cd-e48a924434f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_70a00b66-fa73-4860-b9e4-dd1605fbf76a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_b2f56a62-027b-475a-9793-d7268bdd5441" xlink:to="loc_us-gaap_NondesignatedMember_70a00b66-fa73-4860-b9e4-dd1605fbf76a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="extended" id="if431d72b1d46402199779d312386c00e_DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_6693a1dc-935e-4b9e-b323-5908fb1f3d37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_ffdb7ebe-9bcf-429a-96ed-dca4a3655f69" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6693a1dc-935e-4b9e-b323-5908fb1f3d37" xlink:to="loc_us-gaap_DerivativeNotionalAmount_ffdb7ebe-9bcf-429a-96ed-dca4a3655f69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_d96d81ff-2eda-4c7f-9a68-165afdcf8eca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6693a1dc-935e-4b9e-b323-5908fb1f3d37" xlink:to="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_d96d81ff-2eda-4c7f-9a68-165afdcf8eca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e9afd57d-219b-4bbe-a7cf-721aef8e86c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6693a1dc-935e-4b9e-b323-5908fb1f3d37" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e9afd57d-219b-4bbe-a7cf-721aef8e86c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_6d72517f-e611-48f0-81df-81c026e8af07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_6693a1dc-935e-4b9e-b323-5908fb1f3d37" xlink:to="loc_us-gaap_DerivativeTable_6d72517f-e611-48f0-81df-81c026e8af07" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8ae14d02-01ae-477f-acb1-5a77f4724d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InformationByCategoryOfDebtSecurityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6d72517f-e611-48f0-81df-81c026e8af07" xlink:to="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8ae14d02-01ae-477f-acb1-5a77f4724d1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_8ae14d02-01ae-477f-acb1-5a77f4724d1b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8ae14d02-01ae-477f-acb1-5a77f4724d1b" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_8ae14d02-01ae-477f-acb1-5a77f4724d1b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_c43def1a-c36a-4aeb-97a6-1b8e845b2627" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InformationByCategoryOfDebtSecurityAxis_8ae14d02-01ae-477f-acb1-5a77f4724d1b" xlink:to="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_c43def1a-c36a-4aeb-97a6-1b8e845b2627" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_f7cadcb4-0dbc-44c6-b9d4-a04ae83e3dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableforsaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_c43def1a-c36a-4aeb-97a6-1b8e845b2627" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_f7cadcb4-0dbc-44c6-b9d4-a04ae83e3dd3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_ab14ceea-ac6e-445c-8d29-750705626186" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6d72517f-e611-48f0-81df-81c026e8af07" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_ab14ceea-ac6e-445c-8d29-750705626186" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ab14ceea-ac6e-445c-8d29-750705626186_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_ab14ceea-ac6e-445c-8d29-750705626186" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ab14ceea-ac6e-445c-8d29-750705626186_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1c05d183-1217-4acd-8a10-a43509718c59" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_ab14ceea-ac6e-445c-8d29-750705626186" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1c05d183-1217-4acd-8a10-a43509718c59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_0c733d9e-2e94-47ff-891d-c4b30cf71158" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1c05d183-1217-4acd-8a10-a43509718c59" xlink:to="loc_us-gaap_InterestRateSwapMember_0c733d9e-2e94-47ff-891d-c4b30cf71158" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_e179f3ab-7717-4a16-b312-fecc89a02797" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6d72517f-e611-48f0-81df-81c026e8af07" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_e179f3ab-7717-4a16-b312-fecc89a02797" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_e179f3ab-7717-4a16-b312-fecc89a02797_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_e179f3ab-7717-4a16-b312-fecc89a02797" xlink:to="loc_us-gaap_HedgingRelationshipDomain_e179f3ab-7717-4a16-b312-fecc89a02797_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_c8d7a004-d3d8-4bcb-8d4d-2925da50f97a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_e179f3ab-7717-4a16-b312-fecc89a02797" xlink:to="loc_us-gaap_HedgingRelationshipDomain_c8d7a004-d3d8-4bcb-8d4d-2925da50f97a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_09e3a30d-4778-4e1b-b94b-e2e666cf86f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_c8d7a004-d3d8-4bcb-8d4d-2925da50f97a" xlink:to="loc_us-gaap_CashFlowHedgingMember_09e3a30d-4778-4e1b-b94b-e2e666cf86f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_04528b56-c1f4-4c3f-9a86-6bcf86c1d660" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_c8d7a004-d3d8-4bcb-8d4d-2925da50f97a" xlink:to="loc_us-gaap_FairValueHedgingMember_04528b56-c1f4-4c3f-9a86-6bcf86c1d660" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/FairValueMeasurementRecurringandNonrecurringBasisDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#FairValueMeasurementRecurringandNonrecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/FairValueMeasurementRecurringandNonrecurringBasisDetails" xlink:type="extended" id="ieb086609f5a44d3da279693021dc363d_FairValueMeasurementRecurringandNonrecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_88a6eb53-4b8e-461b-b9d9-184ee52e1610" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_88a6eb53-4b8e-461b-b9d9-184ee52e1610" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCost_34200a82-eba8-4f19-9654-feac306aa475" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquitySecuritiesFvNiCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCost_34200a82-eba8-4f19-9654-feac306aa475" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_16257805-9658-4f3a-bffe-bdf7b68799d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_DerivativeAssets_16257805-9658-4f3a-bffe-bdf7b68799d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_6664cf34-0fce-4fc6-9b2b-d2463eb861cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_DerivativeLiabilities_6664cf34-0fce-4fc6-9b2b-d2463eb861cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeclosedAssets_b7244c27-e443-441e-bd5e-7666ebd4ba2d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ForeclosedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_ForeclosedAssets_b7244c27-e443-441e-bd5e-7666ebd4ba2d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_46041d8c-083d-4f37-aead-d6c35ee1538d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ImpairedFinancingReceivableRecordedInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_46041d8c-083d-4f37-aead-d6c35ee1538d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_b4c59913-e695-4d71-9006-9863252fa780" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_b4c59913-e695-4d71-9006-9863252fa780" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_8d471b7b-ed89-4fd2-8ecc-c33b67170f54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_8d471b7b-ed89-4fd2-8ecc-c33b67170f54" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_ba6d72cb-2ef7-4f39-97f1-ecff0dddc8e3" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_36e640da-2ed8-4616-ad63-00f5aeab7e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e6dcb4bd-77ae-475a-aad5-ec966e7fbb45" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_36e640da-2ed8-4616-ad63-00f5aeab7e5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_65554aca-97ac-4146-a32c-9d3b35c51762" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_36e640da-2ed8-4616-ad63-00f5aeab7e5b" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_65554aca-97ac-4146-a32c-9d3b35c51762" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_a6b4bbc3-349d-41e6-92b0-91fb4d3c86eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_36e640da-2ed8-4616-ad63-00f5aeab7e5b" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_a6b4bbc3-349d-41e6-92b0-91fb4d3c86eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_62f9a853-aa90-425c-aafb-df88ad3760e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_62f9a853-aa90-425c-aafb-df88ad3760e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_62f9a853-aa90-425c-aafb-df88ad3760e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_62f9a853-aa90-425c-aafb-df88ad3760e3" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_62f9a853-aa90-425c-aafb-df88ad3760e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_4f07ad17-b35a-48a0-9eec-6e59d03a5a05" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_62f9a853-aa90-425c-aafb-df88ad3760e3" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_4f07ad17-b35a-48a0-9eec-6e59d03a5a05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6abb4396-625b-4db5-baa2-a30db292541a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_4f07ad17-b35a-48a0-9eec-6e59d03a5a05" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6abb4396-625b-4db5-baa2-a30db292541a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_00285220-2b77-4901-baff-09bfbd7d775c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_4f07ad17-b35a-48a0-9eec-6e59d03a5a05" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_00285220-2b77-4901-baff-09bfbd7d775c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_17fc605e-0bee-4ab2-a5e6-3d5983e2d301" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_4f07ad17-b35a-48a0-9eec-6e59d03a5a05" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_17fc605e-0bee-4ab2-a5e6-3d5983e2d301" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd32139-d841-47ef-8d2f-4e3362413c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd32139-d841-47ef-8d2f-4e3362413c0e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bbd32139-d841-47ef-8d2f-4e3362413c0e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd32139-d841-47ef-8d2f-4e3362413c0e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bbd32139-d841-47ef-8d2f-4e3362413c0e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a386a7eb-430a-4583-8c40-f1746c5af687" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd32139-d841-47ef-8d2f-4e3362413c0e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a386a7eb-430a-4583-8c40-f1746c5af687" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_d4c98ff2-dc15-4ab6-83c1-4244421e2ca5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a386a7eb-430a-4583-8c40-f1746c5af687" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_d4c98ff2-dc15-4ab6-83c1-4244421e2ca5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_48b3f3f7-cc9e-459c-bd3f-7d902e8c5709" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a386a7eb-430a-4583-8c40-f1746c5af687" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_48b3f3f7-cc9e-459c-bd3f-7d902e8c5709" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_0eed5258-120d-4749-b933-137ebffd1b5a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a386a7eb-430a-4583-8c40-f1746c5af687" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_0eed5258-120d-4749-b933-137ebffd1b5a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_fad4af22-ee93-4205-b14c-0e8d581854e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:to="loc_us-gaap_FinancialInstrumentAxis_fad4af22-ee93-4205-b14c-0e8d581854e9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fad4af22-ee93-4205-b14c-0e8d581854e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fad4af22-ee93-4205-b14c-0e8d581854e9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fad4af22-ee93-4205-b14c-0e8d581854e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_fad4af22-ee93-4205-b14c-0e8d581854e9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_146482b8-0b39-4a04-9ae1-6c59972e437d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_146482b8-0b39-4a04-9ae1-6c59972e437d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_c77f2d50-b48f-4faf-a764-894be66d0378" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_c77f2d50-b48f-4faf-a764-894be66d0378" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_ced28dcb-ed29-4afa-90c3-d4a3bfadcf16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_ced28dcb-ed29-4afa-90c3-d4a3bfadcf16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01e63a0c-8b4c-4d1d-81c8-fb2472651d75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_01e63a0c-8b4c-4d1d-81c8-fb2472651d75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_69bd8c56-d530-4c94-bb77-ef1fc8c24540" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_69bd8c56-d530-4c94-bb77-ef1fc8c24540" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_21d07d3e-fa61-48d2-a945-663066add19e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ebcbcc5-f6a5-4a31-ae3c-cc061541c1a9" xlink:to="loc_us-gaap_InterestRateSwapMember_21d07d3e-fa61-48d2-a945-663066add19e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_51a87350-29c5-4584-b377-8a29aaf83910" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_eb167546-e94a-4e9a-bba4-a4c457dd9ca3" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_51a87350-29c5-4584-b377-8a29aaf83910" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_51a87350-29c5-4584-b377-8a29aaf83910_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_51a87350-29c5-4584-b377-8a29aaf83910" xlink:to="loc_us-gaap_ReceivableTypeDomain_51a87350-29c5-4584-b377-8a29aaf83910_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_7c7a457c-3323-4389-af9d-e493e19e993c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_51a87350-29c5-4584-b377-8a29aaf83910" xlink:to="loc_us-gaap_ReceivableTypeDomain_7c7a457c-3323-4389-af9d-e493e19e993c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_CollateralDependentLoansMember_bc757791-74ce-4f8a-a82e-1675568b2378" xlink:href="sbsi-20230331.xsd#sbsi_CollateralDependentLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_7c7a457c-3323-4389-af9d-e493e19e993c" xlink:to="loc_sbsi_CollateralDependentLoansMember_bc757791-74ce-4f8a-a82e-1675568b2378" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/FairValueMeasurementBalanceSheetGroupingDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#FairValueMeasurementBalanceSheetGroupingDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/FairValueMeasurementBalanceSheetGroupingDetails" xlink:type="extended" id="ic56853d2e9ed40ae889691090945445e_FairValueMeasurementBalanceSheetGroupingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a5ce634e-b4d9-4cfb-967f-7afa33b8a6b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a5ce634e-b4d9-4cfb-967f-7afa33b8a6b3" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_2729269c-4eb6-49d8-b51e-63f5f6f02afb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_2729269c-4eb6-49d8-b51e-63f5f6f02afb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosureAbstract_659575e9-499d-4813-a596-9c4e2d9bf17b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosureAbstract_659575e9-499d-4813-a596-9c4e2d9bf17b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_InvestmentSecuritiesHeldtomaturitySecuritiesFairValueDisclosure_b9e9976b-15c4-4012-a7c0-7691a719b95a" xlink:href="sbsi-20230331.xsd#sbsi_InvestmentSecuritiesHeldtomaturitySecuritiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsFairValueDisclosureAbstract_659575e9-499d-4813-a596-9c4e2d9bf17b" xlink:to="loc_sbsi_InvestmentSecuritiesHeldtomaturitySecuritiesFairValueDisclosure_b9e9976b-15c4-4012-a7c0-7691a719b95a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_MortgageBackedAndRelatedSecuritiesAbstract_bfe91578-4844-4a50-8768-13830de15ba8" xlink:href="sbsi-20230331.xsd#sbsi_MortgageBackedAndRelatedSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_sbsi_MortgageBackedAndRelatedSecuritiesAbstract_bfe91578-4844-4a50-8768-13830de15ba8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure_37d2dba9-0d90-4f08-8124-dcf655c3427a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sbsi_MortgageBackedAndRelatedSecuritiesAbstract_bfe91578-4844-4a50-8768-13830de15ba8" xlink:to="loc_us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure_37d2dba9-0d90-4f08-8124-dcf655c3427a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure_ac0d96d5-91bf-4ce9-87fb-67f6e3691257" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure_ac0d96d5-91bf-4ce9-87fb-67f6e3691257" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_72bddd0c-cc0a-4a12-8eb3-e2b09f1ffcc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_72bddd0c-cc0a-4a12-8eb3-e2b09f1ffcc5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_b1f1e554-5039-4e6e-8bd2-2206d62bc3c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_b1f1e554-5039-4e6e-8bd2-2206d62bc3c8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_c0f1344b-f684-4f39-8f80-c4eb695ee694" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_05ff4126-b19a-484e-bbe0-ec7c7a381e02" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_c0f1344b-f684-4f39-8f80-c4eb695ee694" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a5ce634e-b4d9-4cfb-967f-7afa33b8a6b3" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsFairValueDisclosure_1d73cb82-1791-4dac-986f-edd7ed8e8f1e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepositsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:to="loc_us-gaap_DepositsFairValueDisclosure_1d73cb82-1791-4dac-986f-edd7ed8e8f1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure_e38ece77-6623-426c-ae0e-3b42813a7043" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure_e38ece77-6623-426c-ae0e-3b42813a7043" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure_c55cf628-4071-49e9-8412-1ab91159623a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:to="loc_us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure_c55cf628-4071-49e9-8412-1ab91159623a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations_0126ded7-8eb8-4b31-b5ad-ac27983617f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations_0126ded7-8eb8-4b31-b5ad-ac27983617f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_6b497ad0-85c0-4bcf-b2d2-897d0d3427f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_c10b0575-8814-4a39-b814-f6b3ff80fb8a" xlink:to="loc_us-gaap_DebtInstrumentFairValue_6b497ad0-85c0-4bcf-b2d2-897d0d3427f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_91152643-7cfc-429b-b9f7-4a1645de79f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a5ce634e-b4d9-4cfb-967f-7afa33b8a6b3" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_91152643-7cfc-429b-b9f7-4a1645de79f1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_bcadca33-c223-49c9-b5fd-c700493347b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_91152643-7cfc-429b-b9f7-4a1645de79f1" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_bcadca33-c223-49c9-b5fd-c700493347b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_bcadca33-c223-49c9-b5fd-c700493347b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_bcadca33-c223-49c9-b5fd-c700493347b4" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_bcadca33-c223-49c9-b5fd-c700493347b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cdb90af9-0213-4235-b03d-8bdd6048ad90" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_bcadca33-c223-49c9-b5fd-c700493347b4" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cdb90af9-0213-4235-b03d-8bdd6048ad90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_99a9428a-641e-4a44-8d0d-be0fb05ca1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cdb90af9-0213-4235-b03d-8bdd6048ad90" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_99a9428a-641e-4a44-8d0d-be0fb05ca1e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_67554972-2340-4d95-8033-8fea0a30abf6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cdb90af9-0213-4235-b03d-8bdd6048ad90" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_67554972-2340-4d95-8033-8fea0a30abf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_70ab7046-c8af-4304-a150-fb21bf030e26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_cdb90af9-0213-4235-b03d-8bdd6048ad90" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_70ab7046-c8af-4304-a150-fb21bf030e26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_62ea27d7-50c7-4d00-802f-9300e79cd89f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_91152643-7cfc-429b-b9f7-4a1645de79f1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_62ea27d7-50c7-4d00-802f-9300e79cd89f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62ea27d7-50c7-4d00-802f-9300e79cd89f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_62ea27d7-50c7-4d00-802f-9300e79cd89f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62ea27d7-50c7-4d00-802f-9300e79cd89f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_98f5ec2f-ad03-486a-8128-cdec547f008b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_62ea27d7-50c7-4d00-802f-9300e79cd89f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_98f5ec2f-ad03-486a-8128-cdec547f008b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_d58206af-8fed-4358-9e4a-1b2b184646f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_98f5ec2f-ad03-486a-8128-cdec547f008b" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_d58206af-8fed-4358-9e4a-1b2b184646f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_5aa30a46-a496-4334-851d-1e21931ca36d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_98f5ec2f-ad03-486a-8128-cdec547f008b" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_5aa30a46-a496-4334-851d-1e21931ca36d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_3d80bc59-0cd9-4fe5-b0d8-6ac4338f4041" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_98f5ec2f-ad03-486a-8128-cdec547f008b" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_3d80bc59-0cd9-4fe5-b0d8-6ac4338f4041" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/FairValueMeasurementNarrativeDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#FairValueMeasurementNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/FairValueMeasurementNarrativeDetails" xlink:type="extended" id="i37dbcdfa267f42c298adbaceacf3becd_FairValueMeasurementNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d4be5605-9e53-4362-9015-4a3320405f9f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sbsi_NumberofThirdPartySourcesUsedtoValidatePrices_9aa5f273-285d-4a74-b828-7e515df629f8" xlink:href="sbsi-20230331.xsd#sbsi_NumberofThirdPartySourcesUsedtoValidatePrices"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d4be5605-9e53-4362-9015-4a3320405f9f" xlink:to="loc_sbsi_NumberofThirdPartySourcesUsedtoValidatePrices_9aa5f273-285d-4a74-b828-7e515df629f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_2c555998-6d99-4772-ac33-99e5dfef6b44" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d4be5605-9e53-4362-9015-4a3320405f9f" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_2c555998-6d99-4772-ac33-99e5dfef6b44" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_c124e12f-c9d9-4d1e-87ef-95acd64e0923" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_2c555998-6d99-4772-ac33-99e5dfef6b44" xlink:to="loc_us-gaap_FinancialInstrumentAxis_c124e12f-c9d9-4d1e-87ef-95acd64e0923" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c124e12f-c9d9-4d1e-87ef-95acd64e0923_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c124e12f-c9d9-4d1e-87ef-95acd64e0923" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c124e12f-c9d9-4d1e-87ef-95acd64e0923_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8572503d-daa8-49fd-82f1-4dd8b33849ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c124e12f-c9d9-4d1e-87ef-95acd64e0923" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8572503d-daa8-49fd-82f1-4dd8b33849ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_f2cd2d4e-e4e7-4c0e-bfee-653989263edc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableforsaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8572503d-daa8-49fd-82f1-4dd8b33849ed" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_f2cd2d4e-e4e7-4c0e-bfee-653989263edc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_e957848e-a42d-40b8-997d-d740c134d195" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8572503d-daa8-49fd-82f1-4dd8b33849ed" xlink:to="loc_us-gaap_DerivativeMember_e957848e-a42d-40b8-997d-d740c134d195" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.southside.com/role/OffBalanceSheetArrangementsCommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="sbsi-20230331.xsd#OffBalanceSheetArrangementsCommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.southside.com/role/OffBalanceSheetArrangementsCommitmentsandContingenciesDetails" xlink:type="extended" id="i659a2a61c3974be3928e00af01cb74e4_OffBalanceSheetArrangementsCommitmentsandContingenciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_efa6a117-acf1-4cbc-b790-59673ec0a284" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability_c65e4210-33c7-4a37-bcf0-3f44e70bcfbb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_efa6a117-acf1-4cbc-b790-59673ec0a284" xlink:to="loc_us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability_c65e4210-33c7-4a37-bcf0-3f44e70bcfbb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_fcb0d2b6-d95d-4259-be8d-54331f916f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_efa6a117-acf1-4cbc-b790-59673ec0a284" xlink:to="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_fcb0d2b6-d95d-4259-be8d-54331f916f9e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_fcb0d2b6-d95d-4259-be8d-54331f916f9e" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6d1eccaa-2a1e-45d4-ad22-df0d5dbd28c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e7bfa019-d2cc-4c9d-a3d9-fe8b95aca28b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6d1eccaa-2a1e-45d4-ad22-df0d5dbd28c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsToExtendCreditMember_fd4576e7-df11-4a85-91d9-d5efca2de332" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsToExtendCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6d1eccaa-2a1e-45d4-ad22-df0d5dbd28c3" xlink:to="loc_us-gaap_CommitmentsToExtendCreditMember_fd4576e7-df11-4a85-91d9-d5efca2de332" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_6314b9d5-9ff9-4d1f-a3f1-036cb6308e46" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6d1eccaa-2a1e-45d4-ad22-df0d5dbd28c3" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_6314b9d5-9ff9-4d1f-a3f1-036cb6308e46" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
