<SEC-DOCUMENT>0001179110-21-006578.txt : 20210611
<SEC-HEADER>0001179110-21-006578.hdr.sgml : 20210611
<ACCEPTANCE-DATETIME>20210611152959
ACCESSION NUMBER:		0001179110-21-006578
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210609
FILED AS OF DATE:		20210611
DATE AS OF CHANGE:		20210611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			STEINMETZ HENRI
		CENTRAL INDEX KEY:			0001207044

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36473
		FILM NUMBER:		211011106

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Trinseo S.A.
		CENTRAL INDEX KEY:			0001519061
		STANDARD INDUSTRIAL CLASSIFICATION:	PLASTICS, MATERIALS, SYNTH RESINS & NONVULCAN ELASTOMERS [2821]
		IRS NUMBER:				000000000
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1000 CHESTERBROOK BOULEVARD
		STREET 2:		SUITE 3000
		CITY:			BERWYN
		STATE:			PA
		ZIP:			19312
		BUSINESS PHONE:		610-240-3200

	MAIL ADDRESS:	
		STREET 1:		1000 CHESTERBROOK BOULEVARD
		STREET 2:		SUITE 3000
		CITY:			BERWYN
		STATE:			PA
		ZIP:			19312

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Bain Capital Everest (Luxco 2) S.a r.l.
		DATE OF NAME CHANGE:	20110426
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-06-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001519061</issuerCik>
        <issuerName>Trinseo S.A.</issuerName>
        <issuerTradingSymbol>TSE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001207044</rptOwnerCik>
            <rptOwnerName>STEINMETZ HENRI</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TRINSEO S.A.</rptOwnerStreet1>
            <rptOwnerStreet2>1000 CHESTERBROOK BOULEVARD, SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>BERWYN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19312</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2021-06-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>991</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>64.87</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25024</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares withheld by the Company to pay taxes due following the vesting of previously granted restricted stock units.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Angelo Chaclas, attorney-in-fact</signatureName>
        <signatureDate>2021-06-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
