<SEC-DOCUMENT>0001214659-14-001682.txt : 20140304
<SEC-HEADER>0001214659-14-001682.hdr.sgml : 20140304
<ACCEPTANCE-DATETIME>20140304120702
ACCESSION NUMBER:		0001214659-14-001682
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20140303
FILED AS OF DATE:		20140304
DATE AS OF CHANGE:		20140304

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			KCG Holdings, Inc.
		CENTRAL INDEX KEY:			0001569391
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		545 WASHINGTON BOULEVARD
		CITY:			JERSEY CITY
		STATE:			NJ
		ZIP:			07310
		BUSINESS PHONE:		201-222-9400

	MAIL ADDRESS:	
		STREET 1:		545 WASHINGTON BOULEVARD
		CITY:			JERSEY CITY
		STATE:			NJ
		ZIP:			07310

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Knight Holdco, Inc.
		DATE OF NAME CHANGE:	20130211

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Limestone Merger Sub LLC
		CENTRAL INDEX KEY:			0001593504
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-54991
		FILM NUMBER:		14663391

	BUSINESS ADDRESS:	
		STREET 1:		315 PARK AVENUE SOUTH
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10010
		BUSINESS PHONE:		212 460-1900

	MAIL ADDRESS:	
		STREET 1:		315 PARK AVENUE SOUTH
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10010

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LEUCADIA NATIONAL CORP
		CENTRAL INDEX KEY:			0000096223
		STANDARD INDUSTRIAL CLASSIFICATION:	MEAT PACKING PLANTS [2011]
		STATE OF INCORPORATION:			NY
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-54991
		FILM NUMBER:		14663392

	BUSINESS ADDRESS:	
		STREET 1:		520 MADISON AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		2124601900

	MAIL ADDRESS:	
		STREET 1:		520 MADISON AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

	FORMER NAME:	
		FORMER CONFORMED NAME:	TALCOTT NATIONAL CORP
		DATE OF NAME CHANGE:	19800603

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Jefferies Group LLC
		CENTRAL INDEX KEY:			0001084580
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1130

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-54991
		FILM NUMBER:		14663393

	BUSINESS ADDRESS:	
		STREET 1:		520 MADISON AVENUE
		STREET 2:		12TH FLOOR
		CITY:			NEW  YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		212-284-2550

	MAIL ADDRESS:	
		STREET 1:		520 MADISON AVENUE
		STREET 2:		12TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

	FORMER NAME:	
		FORMER CONFORMED NAME:	JEFFERIES GROUP INC /DE/
		DATE OF NAME CHANGE:	19990429

	FORMER NAME:	
		FORMER CONFORMED NAME:	JEF HOLDING CO INC
		DATE OF NAME CHANGE:	19990419

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JEFFERIES LLC
		CENTRAL INDEX KEY:			0001265287
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1130

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-54991
		FILM NUMBER:		14663394

	BUSINESS ADDRESS:	
		STREET 1:		520 MADISON AVE.
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		3109141373

	MAIL ADDRESS:	
		STREET 1:		520 MADISON AVE.
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

	FORMER NAME:	
		FORMER CONFORMED NAME:	JEFFERIES & COMPANY, INC.
		DATE OF NAME CHANGE:	20040518

	FORMER NAME:	
		FORMER CONFORMED NAME:	JEFFERIES & CO INC
		DATE OF NAME CHANGE:	20030930
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>marketforms-22768.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-03-03</periodOfReport>

    <issuer>
        <issuerCik>0001569391</issuerCik>
        <issuerName>KCG Holdings, Inc.</issuerName>
        <issuerTradingSymbol>KCG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001265287</rptOwnerCik>
            <rptOwnerName>JEFFERIES LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>520 MADISON AVE.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001084580</rptOwnerCik>
            <rptOwnerName>Jefferies Group LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>520 MADISON AVE.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000096223</rptOwnerCik>
            <rptOwnerName>LEUCADIA NATIONAL CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>520 MADISON AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001593504</rptOwnerCik>
            <rptOwnerName>Limestone Merger Sub LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O JEFFERIES</rptOwnerStreet1>
            <rptOwnerStreet2>520 MADISON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-03-03</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6000000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22467774</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Roland T. Kelly, Associate General Counsel</signatureName>
        <signatureDate>2014-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Roland T. Kelly, Associate General Counsel</signatureName>
        <signatureDate>2014-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Roland T. Kelly, Associate General Counsel</signatureName>
        <signatureDate>2014-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Roland T. Kelly, Authorized Person</signatureName>
        <signatureDate>2014-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
