<SEC-DOCUMENT>0001567619-21-000698.txt : 20210107
<SEC-HEADER>0001567619-21-000698.hdr.sgml : 20210107
<ACCEPTANCE-DATETIME>20210107110911
ACCESSION NUMBER:		0001567619-21-000698
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210106
FILED AS OF DATE:		20210107
DATE AS OF CHANGE:		20210107

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			M&G INVESTMENT MANAGEMENT LTD
		CENTRAL INDEX KEY:			0000922898

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36473
		FILM NUMBER:		21513396

	BUSINESS ADDRESS:	
		STREET 1:		10 FENCHURCH AVENUE
		CITY:			LONDON
		STATE:			X0
		ZIP:			EC3M 5AG
		BUSINESS PHONE:		02075482293

	MAIL ADDRESS:	
		STREET 1:		10 FENCHURCH AVENUE
		CITY:			LONDON
		STATE:			X0
		ZIP:			EC3M 5AG

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>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-01-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000922898</rptOwnerCik>
            <rptOwnerName>M&amp;G INVESTMENT MANAGEMENT LTD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 FENCHURCH AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>EC3M 5AG</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-01-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>55.43</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7752044</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Please see footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-01-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>55.88</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7747044</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Please see footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The reported securities are held directly by certain funds advised by M&amp;G Investment Management Limited, (i) M&amp;G (Lux) Investment Funds 1 holds 2,551,620 ordinary shares in Trinseo S.A.; (ii) M&amp;G Global Dividend Fund directly holds 3,615,353 ordinary shares in Trinseo S.A.; and (iii) LF Access Global Dividend Fund directly holds 1,580,071 ordinary shares in Trinseo S.A. The reported securities may be deemed beneficially owned for the purposes of Section 13(d) of the Securities Exchange Act 1934 by M&amp;G Investment Management Limited as investment manager to these funds. The Reporting Person disclaims beneficial ownership of the securities for purposes of Rule 16a-1(a) (2) and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ M&amp;G INVESTMENT MANAGEMENT LIMITED, By: Tamara Postoj, Head of Regulatory Reporting</signatureName>
        <signatureDate>2021-01-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
