<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/nport" xmlns:com="http://www.sec.gov/edgar/common" xmlns:ncom="http://www.sec.gov/edgar/nportcommon" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sec.gov/edgar/nport eis_NPORT_Filer.xsd">
  <headerData>
    <submissionType>NPORT-P</submissionType>
    <isConfidential>false</isConfidential>
    <filerInfo>

      <filer>
        <issuerCredentials>
          <cik>0001330967</cik>
          <ccc>XXXXXXXX</ccc>
        </issuerCredentials>
      </filer>


      <seriesClassInfo>
        <seriesId>S000002501</seriesId>
        <classId>C000006793</classId>
        <classId>C000006794</classId>
        <classId>C000006795</classId>
        <classId>C000006796</classId>
        <classId>C000006797</classId>
        <classId>C000006799</classId>
        <classId>C000006800</classId>
        <classId>C000006801</classId>
        <classId>C000173225</classId>
      </seriesClassInfo>


    </filerInfo>
  </headerData>
  <formData>
    <genInfo>
      <regName>MFS SERIES TRUST XII</regName>
      <regFileNumber>811-21780</regFileNumber>
      <regCik>0001330967</regCik>
      <regLei>549300VVIIPRJRW6FR46</regLei>
      <regStreet1>111 HUNTINGTON AVENUE</regStreet1>
      <regCity>BOSTON</regCity>
      <regStateConditional regCountry="US" regState="US-MA"/>
      <regZipOrPostalCode>02199</regZipOrPostalCode>
      <regPhone>617-954-5000</regPhone>
      <seriesName>MFS Lifetime Income Fund</seriesName>
      <seriesId>S000002501</seriesId>
      <seriesLei>HVSHYLXT64G65WN2P306</seriesLei>
      <repPdEnd>2026-04-30</repPdEnd>
      <repPdDate>2026-01-31</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>521688969.44</totAssets>
      <totLiabs>1314584.84</totLiabs>
      <netAssets>520374384.60</netAssets>
      <assetsAttrMiscSec>0.00000000</assetsAttrMiscSec>
      <assetsInvested>0.00000000</assetsInvested>
      <amtPayOneYrBanksBorr>0.00000000</amtPayOneYrBanksBorr>
      <amtPayOneYrCtrldComp>0.00000000</amtPayOneYrCtrldComp>
      <amtPayOneYrOthAffil>0.00000000</amtPayOneYrOthAffil>
      <amtPayOneYrOther>0.00000000</amtPayOneYrOther>
      <amtPayAftOneYrBanksBorr>0.00000000</amtPayAftOneYrBanksBorr>
      <amtPayAftOneYrCtrldComp>0.00000000</amtPayAftOneYrCtrldComp>
      <amtPayAftOneYrOthAffil>0.00000000</amtPayAftOneYrOthAffil>
      <amtPayAftOneYrOther>0.00000000</amtPayAftOneYrOther>
      <delayDeliv>0.00000000</delayDeliv>
      <standByCommit>0.00000000</standByCommit>
      <liquidPref>0.00000000</liquidPref>
      <cshNotRptdInCorD>0.00000000</cshNotRptdInCorD>
      <isNonCashCollateral>N</isNonCashCollateral>
      <returnInfo>
        <monthlyTotReturns>
          <monthlyTotReturn classId="C000006793" rtn1="0.67000000" rtn2="0.07000000" rtn3="1.25000000"/>
          <monthlyTotReturn classId="C000006794" rtn1="0.60000000" rtn2="0.01000000" rtn3="1.19000000"/>
          <monthlyTotReturn classId="C000006795" rtn1="0.53000000" rtn2="0.01000000" rtn3="1.19000000"/>
          <monthlyTotReturn classId="C000006796" rtn1="0.69000000" rtn2="0.09000000" rtn3="1.27000000"/>
          <monthlyTotReturn classId="C000006797" rtn1="0.60000000" rtn2="0.01000000" rtn3="1.18000000"/>
          <monthlyTotReturn classId="C000006799" rtn1="0.65000000" rtn2="0.05000000" rtn3="1.23000000"/>
          <monthlyTotReturn classId="C000006800" rtn1="0.67000000" rtn2="0.07000000" rtn3="1.25000000"/>
          <monthlyTotReturn classId="C000006801" rtn1="0.69000000" rtn2="0.09000000" rtn3="1.27000000"/>
          <monthlyTotReturn classId="C000173225" rtn1="0.70000000" rtn2="0.10000000" rtn3="1.28000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="430871.28000000" netUnrealizedAppr="1919664.04000000"/>
        <othMon2 netRealizedGain="1049369.53000000" netUnrealizedAppr="-14110391.73000000"/>
        <othMon3 netRealizedGain="551675.30000000" netUnrealizedAppr="4962191.91000000"/>
      </returnInfo>
      <mon1Flow redemption="11393138.07000000" reinvestment="1263663.41000000" sales="2489491.13000000"/>
      <mon2Flow redemption="12521405.17000000" reinvestment="12106337.54000000" sales="5670370.51000000"/>
      <mon3Flow redemption="16176422.21000000" reinvestment="4344197.44000000" sales="4484097.98000000"/>



    </fundInfo>
    <invstOrSecs>
      <invstOrSec>
        <name>MFS New Discovery Fund</name>
        <lei>ZVEMRLDGMDO1D1VDSU87</lei>
        <title>MFS New Discovery Fund</title>
        <cusip>55273H346</cusip>
        <identifiers>
          <isin value="US55273H3460"/>
        </identifiers>
        <balance>68417.74000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>2502036.57000000</valUSD>
        <pctVal>0.480814706496</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Value Fund</name>
        <lei>HV6C0RMURVKFUQ3UTB42</lei>
        <title>MFS Value Fund</title>
        <cusip>55273H353</cusip>
        <identifiers>
          <isin value="US55273H3536"/>
        </identifiers>
        <balance>202420.49000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10436800.46000000</valUSD>
        <pctVal>2.005633015165</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research International Fund</name>
        <lei>UH91KW1VFNZQF5FY7237</lei>
        <title>MFS Research International Fund</title>
        <cusip>55273H361</cusip>
        <identifiers>
          <isin value="US55273H3619"/>
        </identifiers>
        <balance>316880.78000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8644507.71000000</valUSD>
        <pctVal>1.661209307342</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Mid Cap Value Fund</name>
        <lei>BXHSCSBXYY1DOHP6E209</lei>
        <title>MFS Mid Cap Value Fund</title>
        <cusip>55273W475</cusip>
        <identifiers>
          <isin value="US55273W4758"/>
        </identifiers>
        <balance>238880.69000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7751678.42000000</valUSD>
        <pctVal>1.489634895452</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Core Equity Fund</name>
        <lei>SQK3NYUBFBKJ3GF1IO09</lei>
        <title>MFS Blended Research Core Equity Fund</title>
        <cusip>55273W483</cusip>
        <identifiers>
          <isin value="US55273W4832"/>
        </identifiers>
        <balance>212078.30000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8512823.12000000</valUSD>
        <pctVal>1.635903567110</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Mid Cap Equity Fund</name>
        <lei>549300CJNZTXTE7DBK33</lei>
        <title>MFS Blended Research Mid Cap Equity Fund</title>
        <cusip>552743551</cusip>
        <identifiers>
          <isin value="US5527435516"/>
        </identifiers>
        <balance>1000987.69000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>15345141.26000000</valUSD>
        <pctVal>2.948865607940</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Small Cap Equity Fund</name>
        <lei>549300R0MISDFKQQMH05</lei>
        <title>MFS Blended Research Small Cap Equity Fund</title>
        <cusip>552743684</cusip>
        <identifiers>
          <isin value="US5527436845"/>
        </identifiers>
        <balance>325811.88000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>5043567.93000000</valUSD>
        <pctVal>0.969219100566</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Growth Equity Fund</name>
        <lei>549300M0GLI3GVVPMM34</lei>
        <title>MFS Blended Research Growth Equity Fund</title>
        <cusip>552743783</cusip>
        <identifiers>
          <isin value="US5527437835"/>
        </identifiers>
        <balance>305594.05000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8431339.92000000</valUSD>
        <pctVal>1.620244994664</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Global Opportunistic Bond Fund</name>
        <lei>XE280U8NKIY4V6K1JN70</lei>
        <title>MFS Global Opportunistic Bond Fund</title>
        <cusip>552743882</cusip>
        <identifiers>
          <isin value="US5527438825"/>
        </identifiers>
        <balance>4440003.96000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>36496832.55000000</valUSD>
        <pctVal>7.013572080042</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Value Equity Fund</name>
        <lei>549300QL66OEPI6JSE90</lei>
        <title>MFS Blended Research Value Equity Fund</title>
        <cusip>552746133</cusip>
        <identifiers>
          <isin value="US5527461330"/>
        </identifiers>
        <balance>631880.31000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10438662.70000000</valUSD>
        <pctVal>2.005990880589</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Emerging Markets Debt Local Currency Fund</name>
        <lei>5493001KPK8UJ27DMD68</lei>
        <title>MFS Emerging Markets Debt Local Currency Fund</title>
        <cusip>552746323</cusip>
        <identifiers>
          <isin value="US5527463237"/>
        </identifiers>
        <balance>851792.87000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>5221490.28000000</valUSD>
        <pctVal>1.003410320439</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS International Intrinsic Value Fund</name>
        <lei>7540QFSKYNTDFH7HAK24</lei>
        <title>MFS International Intrinsic Value Fund</title>
        <cusip>552746349</cusip>
        <identifiers>
          <isin value="US5527463492"/>
        </identifiers>
        <balance>62188.12000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>2853190.81000000</valUSD>
        <pctVal>0.548295783658</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS International Growth Fund</name>
        <lei>PTNAY8DC4VJYOKVJ5B83</lei>
        <title>MFS International Growth Fund</title>
        <cusip>552746356</cusip>
        <identifiers>
          <isin value="US5527463567"/>
        </identifiers>
        <balance>57892.32000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>2840197.42000000</valUSD>
        <pctVal>0.545798852528</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Emerging Markets Debt Fund</name>
        <lei>509D6AOZZ4SJ08T5BZ82</lei>
        <title>MFS Emerging Markets Debt Fund</title>
        <cusip>552746364</cusip>
        <identifiers>
          <isin value="US5527463641"/>
        </identifiers>
        <balance>407665.61000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>5222196.41000000</valUSD>
        <pctVal>1.003546016972</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research Bond Fund</name>
        <lei>FJAEEQMSDDUK9QL2E558</lei>
        <title>MFS Research Bond Fund</title>
        <cusip>55274K603</cusip>
        <identifiers>
          <isin value="US55274K6038"/>
        </identifiers>
        <balance>10532711.01000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>101535334.11000000</valUSD>
        <pctVal>19.51197774426</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Ltd Maturity Fund</name>
        <lei>7ER38PJ2TK60L3Y32478</lei>
        <title>MFS Ltd Maturity Fund</title>
        <cusip>55274K801</cusip>
        <identifiers>
          <isin value="US55274K8018"/>
        </identifiers>
        <balance>17681062.49000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>104318268.70000000</valUSD>
        <pctVal>20.04677243676</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Inflation Adjusted Bond Fund</name>
        <lei>VOHO802M9IKG3IZTEN75</lei>
        <title>MFS Inflation Adjusted Bond Fund</title>
        <cusip>55274K884</cusip>
        <identifiers>
          <isin value="US55274K8844"/>
        </identifiers>
        <balance>5751069.35000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>52277220.37000000</valUSD>
        <pctVal>10.04607873044</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Commodity Strategy Fund</name>
        <lei>T0OEQ8I3F6DXUJCOV412</lei>
        <title>MFS Commodity Strategy Fund</title>
        <cusip>55276T826</cusip>
        <identifiers>
          <isin value="US55276T8264"/>
        </identifiers>
        <balance>2623925.54000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10390745.14000000</valUSD>
        <pctVal>1.996782594897</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Institutional Money Market Portfolio</name>
        <lei>5L2W638H85N8T1136O07</lei>
        <title>MFS Institutional Money Market Portfolio</title>
        <cusip>55291X109</cusip>
        <identifiers>
          <isin value="US55291X1090"/>
        </identifiers>
        <balance>7611926.58000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7613448.96000000</valUSD>
        <pctVal>1.463071431898</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research Fund</name>
        <lei>XFPOOG2XVG5TW1LZ8588</lei>
        <title>MFS Research Fund</title>
        <cusip>552981391</cusip>
        <identifiers>
          <isin value="US5529813918"/>
        </identifiers>
        <balance>149692.28000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8487552.33000000</valUSD>
        <pctVal>1.631047296173</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS New Discovery Value Fund</name>
        <lei>LRMRW30Z8FYTIFW1W860</lei>
        <title>MFS New Discovery Value Fund</title>
        <cusip>552982696</cusip>
        <identifiers>
          <isin value="US5529826969"/>
        </identifiers>
        <balance>143253.85000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>2547053.44000000</valUSD>
        <pctVal>0.489465568517</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Government Securities Fund</name>
        <lei>UWWK6TDSOPDQSQMMEB12</lei>
        <title>MFS Government Securities Fund</title>
        <cusip>552982712</cusip>
        <identifiers>
          <isin value="US5529827124"/>
        </identifiers>
        <balance>5992193.68000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>52132085.03000000</valUSD>
        <pctVal>10.01818816851</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Global Real Estate Fund</name>
        <lei>ROYDM6SL56ZXYAENS860</lei>
        <title>MFS Global Real Estate Fund</title>
        <cusip>552982720</cusip>
        <identifiers>
          <isin value="US5529827207"/>
        </identifiers>
        <balance>635905.35000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10486079.16000000</valUSD>
        <pctVal>2.015102870226</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS High Income Fund</name>
        <lei>DMVGFZCV67YA34LSI126</lei>
        <title>MFS High Income Fund</title>
        <cusip>552984684</cusip>
        <identifiers>
          <isin value="US5529846843"/>
        </identifiers>
        <balance>3296027.51000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10382486.64000000</valUSD>
        <pctVal>1.995195564435</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Growth Fund</name>
        <lei>K4ZYIH3WSXKUSPKIPM59</lei>
        <title>MFS Growth Fund</title>
        <cusip>552985673</cusip>
        <identifiers>
          <isin value="US5529856735"/>
        </identifiers>
        <balance>42486.12000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8365517.82000000</valUSD>
        <pctVal>1.607596005408</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research International Equity Fund</name>
        <lei>254900SJDP6D81SAVM86</lei>
        <title>MFS Blended Research International Equity Fund</title>
        <cusip>552987448</cusip>
        <identifiers>
          <isin value="US5529874480"/>
        </identifiers>
        <balance>778072.18000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14425458.12000000</valUSD>
        <pctVal>2.772130709525</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Mid Cap Growth Fund</name>
        <lei>XPX0WXKIO6CLKBLYF666</lei>
        <title>MFS Mid Cap Growth Fund</title>
        <cusip>552987554</cusip>
        <identifiers>
          <isin value="US5529875545"/>
        </identifiers>
        <balance>267551.45000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7561004.03000000</valUSD>
        <pctVal>1.452993124519</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
    </invstOrSecs>
    <explntrNotes>
      <explntrNote note="Monthly returns presented in Item B.5(a) have been calculated without deducting any applicable sales loads or redemption fees." noteItem="B.5.a"/>
    </explntrNotes>
    <signature>
      <ncom:dateSigned>2026-02-27</ncom:dateSigned>
      <ncom:nameOfApplicant>MFS SERIES TRUST XII</ncom:nameOfApplicant>
      <ncom:signature>James Byrne</ncom:signature>
      <ncom:signerName>James Byrne</ncom:signerName>
      <ncom:title>Assistant Treasurer</ncom:title>
    </signature>
  </formData>
  <documents>XXXX</documents>
</edgarSubmission>
