<?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>0000783740</cik>
          <ccc>XXXXXXXX</ccc>
        </issuerCredentials>
      </filer>


      <seriesClassInfo>
        <seriesId>S000002507</seriesId>
        <classId>C000006858</classId>
        <classId>C000231059</classId>
        <classId>C000006860</classId>
        <classId>C000006852</classId>
        <classId>C000006857</classId>
        <classId>C000006863</classId>
        <classId>C000006851</classId>
        <classId>C000006856</classId>
        <classId>C000006862</classId>
      </seriesClassInfo>


    </filerInfo>
  </headerData>
  <formData>
    <genInfo>
      <regName>MFS SERIES TRUST X</regName>
      <regFileNumber>811-04492</regFileNumber>
      <regCik>0000783740</regCik>
      <regLei>5493001MUVNRNUPJY164</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 Moderate Allocation Fund</seriesName>
      <seriesId>S000002507</seriesId>
      <seriesLei>6W9PGRTO8WIPR5M6Z061</seriesLei>
      <repPdEnd>2026-05-31</repPdEnd>
      <repPdDate>2026-02-28</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>6573328151.88</totAssets>
      <totLiabs>2683153.51</totLiabs>
      <netAssets>6570644998.37</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="C000006858" rtn1="0.22000000" rtn2="1.92000000" rtn3="1.55000000"/>
          <monthlyTotReturn classId="C000231059" rtn1="0.19000000" rtn2="1.97000000" rtn3="1.55000000"/>
          <monthlyTotReturn classId="C000006860" rtn1="0.10000000" rtn2="1.87000000" rtn3="1.47000000"/>
          <monthlyTotReturn classId="C000006852" rtn1="0.17000000" rtn2="1.91000000" rtn3="1.58000000"/>
          <monthlyTotReturn classId="C000006857" rtn1="0.13000000" rtn2="1.81000000" rtn3="1.52000000"/>
          <monthlyTotReturn classId="C000006863" rtn1="0.19000000" rtn2="1.88000000" rtn3="1.60000000"/>
          <monthlyTotReturn classId="C000006851" rtn1="0.15000000" rtn2="1.91000000" rtn3="1.58000000"/>
          <monthlyTotReturn classId="C000006856" rtn1="0.09000000" rtn2="1.83000000" rtn3="1.50000000"/>
          <monthlyTotReturn classId="C000006862" rtn1="0.12000000" rtn2="1.92000000" rtn3="1.53000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="6320524.30000000" netUnrealizedAppr="-356503352.30000000"/>
        <othMon2 netRealizedGain="1740300.85000000" netUnrealizedAppr="114327049.58000000"/>
        <othMon3 netRealizedGain="4884069.61000000" netUnrealizedAppr="90403961.39000000"/>
      </returnInfo>
      <mon1Flow redemption="151886680.29000000" reinvestment="398119986.70000000" sales="70113818.50000000"/>
      <mon2Flow redemption="121382921.12000000" reinvestment="0.00000000" sales="60995027.72000000"/>
      <mon3Flow redemption="105014384.68000000" reinvestment="0.00000000" sales="52141843.37000000"/>



    </fundInfo>
    <invstOrSecs>
      <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>73327920.28000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>646752256.84000000</valUSD>
        <pctVal>9.843055849166</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>15336978.48000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>197847022.40000000</valUSD>
        <pctVal>3.011074596924</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>12455763.76000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>356733073.94000000</valUSD>
        <pctVal>5.429194151084</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 Equity Fund</name>
        <lei>GLINMRWNKCBOHYKQ2131</lei>
        <title>MFS Emerging Markets Equity Fund</title>
        <cusip>552746331</cusip>
        <identifiers>
          <isin value="US5527463310"/>
        </identifiers>
        <balance>1420673.71000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>71246786.71000000</valUSD>
        <pctVal>1.084319526129</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>2348698.38000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>443903994.58000000</valUSD>
        <pctVal>6.755866352391</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 New Discovery Fund</name>
        <lei>RC53GXLQZ5LVIZBRHR66</lei>
        <title>MFS International New Discovery Fund</title>
        <cusip>552981383</cusip>
        <identifiers>
          <isin value="US5529813835"/>
        </identifiers>
        <balance>1943145.87000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>71138570.15000000</valUSD>
        <pctVal>1.082672556007</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>5462737.14000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>99476443.30000000</valUSD>
        <pctVal>1.513952486014</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>83137402.39000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>260220069.48000000</valUSD>
        <pctVal>3.960342851341</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>2956301.06000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>142523274.01000000</valUSD>
        <pctVal>2.169091071658</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>15372191.03000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>437185112.86000000</valUSD>
        <pctVal>6.653610307183</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>11761101.92000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>204878395.48000000</valUSD>
        <pctVal>3.118086512523</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 Fund</name>
        <lei>ZVEMRLDGMDO1D1VDSU87</lei>
        <title>MFS New Discovery Fund</title>
        <cusip>55273H346</cusip>
        <identifiers>
          <isin value="US55273H3460"/>
        </identifiers>
        <balance>2651782.41000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>97187825.18000000</valUSD>
        <pctVal>1.479121535315</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>83334212.01000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>83342545.43000000</valUSD>
        <pctVal>1.268407370215</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 Large Cap Value Fund</name>
        <lei>549300YEW2NKJCMQAR75</lei>
        <title>MFS International Large Cap Value Fund</title>
        <cusip>552743445</cusip>
        <identifiers>
          <isin value="US5527434451"/>
        </identifiers>
        <balance>7686030.53000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>141576682.27000000</valUSD>
        <pctVal>2.154684696937</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>8363334.36000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>468012190.84000000</valUSD>
        <pctVal>7.122773958357</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>57562156.09000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>561806643.39000000</valUSD>
        <pctVal>8.550251056469</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>39711032.22000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>329601567.42000000</valUSD>
        <pctVal>5.016274163370</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>10107520.55000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>535698588.89000000</valUSD>
        <pctVal>8.152907195912</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>50059609.18000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>461049000.56000000</valUSD>
        <pctVal>7.016799730838</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>50659769.00000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>205678662.13000000</valUSD>
        <pctVal>3.130265935551</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>13948703.86000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>470489781.27000000</valUSD>
        <pctVal>7.160480917576</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>21396170.26000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>132870217.33000000</valUSD>
        <pctVal>2.022179213196</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>2763733.54000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>140508212.97000000</valUSD>
        <pctVal>2.138423442521</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>2026-03-27</ncom:dateSigned>
      <ncom:nameOfApplicant>MFS SERIES TRUST X</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>