<SEC-DOCUMENT>0001708035-25-000122.txt : 20251110
<SEC-HEADER>0001708035-25-000122.hdr.sgml : 20251110
<ACCEPTANCE-DATETIME>20251110160135
ACCESSION NUMBER:		0001708035-25-000122
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20251107
FILED AS OF DATE:		20251110
DATE AS OF CHANGE:		20251110

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ward Susan F
		CENTRAL INDEX KEY:			0001795151
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38221
		FILM NUMBER:		251466025

	MAIL ADDRESS:	
		STREET 1:		11465 JOHNS CREEK PARKWAY, SUITE 400
		CITY:			JOHNS CREEK
		STATE:			GA
		ZIP:			30097

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Ecovyst Inc.
		CENTRAL INDEX KEY:			0001708035
		STANDARD INDUSTRIAL CLASSIFICATION:	CHEMICALS & ALLIED PRODUCTS [2800]
		ORGANIZATION NAME:           	08 Industrial Applications and Services
		EIN:				813406833
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		600 LEE ROAD, SUITE 200
		CITY:			WAYNE
		STATE:			PA
		ZIP:			19087
		BUSINESS PHONE:		484-617-1200

	MAIL ADDRESS:	
		STREET 1:		600 LEE ROAD, SUITE 200
		CITY:			WAYNE
		STATE:			PA
		ZIP:			19087

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PQ Group Holdings Inc.
		DATE OF NAME CHANGE:	20170531
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1762808492.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-11-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001708035</issuerCik>
        <issuerName>Ecovyst Inc.</issuerName>
        <issuerTradingSymbol>ECVT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001795151</rptOwnerCik>
            <rptOwnerName>Ward Susan F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ECOVYST INC.</rptOwnerStreet1>
            <rptOwnerStreet2>600 LEE ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>WAYNE</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19087</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-11-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>15000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.4012</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>78261</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $8.400 to $8.415, inclusive. The reporting person undertakes to provide to Ecovyst Inc., any security holder of Ecovyst Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Joseph S. Koscinski, as attorney-in-fact for Susan F. Ward</signatureName>
        <signatureDate>2025-11-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
