-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Hjn0YqeRmm/jro6NsKyjCHeQvV2BWwM+drANAWOX+L656BP+ICjGC5RwZFzizNU4
 zqySB9/hNJOex814zBts+Q==

<SEC-DOCUMENT>0001179110-03-012711.txt : 20031216
<SEC-HEADER>0001179110-03-012711.hdr.sgml : 20031216
<ACCEPTANCE-DATETIME>20031216123230
ACCESSION NUMBER:		0001179110-03-012711
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031212
FILED AS OF DATE:		20031216

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MAINSOURCE FINANCIAL GROUP
		CENTRAL INDEX KEY:			0000720002
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				351562245
		STATE OF INCORPORATION:			IN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		201 N BROADWAY
		STREET 2:		PO BOX 87
		CITY:			GREENSBURG
		STATE:			IN
		ZIP:			47240
		BUSINESS PHONE:		8126630157

	MAIL ADDRESS:	
		STREET 1:		201 NORTH BROADWAY
		STREET 2:		P O BOX 87
		CITY:			GREENSBURG
		STATE:			IN
		ZIP:			47240

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INDIANA UNITED BANCORP
		DATE OF NAME CHANGE:	19920703

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DEFFNER DALE J
		CENTRAL INDEX KEY:			0001055525

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-12422
		FILM NUMBER:		031056708

	BUSINESS ADDRESS:	
		STREET 1:		9005 HIDDEN VALLEY LANE
		CITY:			BROOKVILLE
		STATE:			IN
		ZIP:			47012
		BUSINESS PHONE:		7656476266

	MAIL ADDRESS:	
		STREET 1:		11013 LAKESIDE TERRACE
		CITY:			BROOKVILLE
		STATE:			IN
		ZIP:			47012
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-12-12</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000720002</issuerCik>
        <issuerName>MAINSOURCE FINANCIAL GROUP</issuerName>
        <issuerTradingSymbol>msfg</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001055525</rptOwnerCik>
            <rptOwnerName>DEFFNER DALE J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>9005 HIDDEN VALLEY LANE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BROOKVILLE</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>47012</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>Common Stock </value>
</securityTitle>
<transactionDate><value>2003-12-12</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>G</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>2787</value>
</transactionShares>
<transactionPricePerShare><value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>135364</value>
<footnoteId id="F1"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
<footnoteId id="F2"></footnoteId>
</directOrIndirectOwnership>
</ownershipNature>
</nonDerivativeTransaction>
<nonDerivativeTransaction><securityTitle><value>Common Stock</value>
</securityTitle>
<transactionDate><value>2003-12-12</value>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>G</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>3123</value>
</transactionShares>
<transactionPricePerShare><value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>135364</value>
<footnoteId id="F1"></footnoteId>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>I</value>
<footnoteId id="F2"></footnoteId>
</directOrIndirectOwnership>
<natureOfOwnership><value>Spouse</value>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeTransaction>
</nonDerivativeTable>
<derivativeTable></derivativeTable>
<footnotes><footnote id="F1">These totals include shares which were acquired through a 5% stock dividend issued January 17, 2003.</footnote>
<footnote id="F2">Summary of Ownership:  Self 56,166; Self/IRA 8,154; Spouse 62,470; Spouse/IRA 8,574.  Total shares 135,364.</footnote>
</footnotes>
<ownerSignature><signatureName>Dale J. Deffner</signatureName>
<signatureDate>2003-12-16</signatureDate>
</ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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