-----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,
 E6gwRYKEIvB6o38UHWjAO11Jj3lPNtFEWAIIwIxGpVpLxPqMiA53hTh56dYlZ1eF
 YpPdNerYIzWb1TPrcRoWpQ==

<SEC-DOCUMENT>0001179110-05-014200.txt : 20050713
<SEC-HEADER>0001179110-05-014200.hdr.sgml : 20050713
<ACCEPTANCE-DATETIME>20050713173414
ACCESSION NUMBER:		0001179110-05-014200
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050711
FILED AS OF DATE:		20050713
DATE AS OF CHANGE:		20050713

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SAFETY INSURANCE GROUP INC
		CENTRAL INDEX KEY:			0001172052
		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
		IRS NUMBER:				134181699
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		20 CUSTOM HOUSE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110
		BUSINESS PHONE:		617-951-0600

	MAIL ADDRESS:	
		STREET 1:		20 CUSTOM HOUSE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SAFETY HOLDINGS INC
		DATE OF NAME CHANGE:	20020424

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BEGLEY WILLIAM J JR
		CENTRAL INDEX KEY:			0001214337

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-50070
		FILM NUMBER:		05953064

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		617-951-0600

	MAIL ADDRESS:	
		STREET 1:		20 CUSTOM HOUSE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-07-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001172052</issuerCik>
        <issuerName>SAFETY INSURANCE GROUP INC</issuerName>
        <issuerTradingSymbol>SAFT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001214337</rptOwnerCik>
            <rptOwnerName>BEGLEY WILLIAM J JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>20 CUSTOM HOUSE STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP, CFO and Secretary</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-07-11</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <deemedExecutionDate>
                <value>2005-07-11</value>
                <footnoteId id="F1"/>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>9000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.0581</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>105496</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-07-12</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <deemedExecutionDate>
                <value>2005-07-12</value>
                <footnoteId id="F1"/>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>9431</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.0613</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>96065</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The sales reported on this form were made pursuant to a written trading plan adopted in accordance with Rule 10b5-1 on 3/16/05.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>William J. Begley, Jr.</signatureName>
        <signatureDate>2005-07-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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