    <SEC-DOCUMENT>0000950170-24-035201-index.html : 20240322
    <SEC-HEADER>0000950170-24-035201.hdr.sgml : 20240322
    <ACCEPTANCE-DATETIME>20240322124422
    ACCESSION NUMBER:		0000950170-24-035201
    CONFORMED SUBMISSION TYPE:	DEFA14A
    PUBLIC DOCUMENT COUNT:		3
    FILED AS OF DATE:		20240322
    DATE AS OF CHANGE:		20240322

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Arthur J. Gallagher & Co.
    		CENTRAL INDEX KEY:			0000354190
    		STANDARD INDUSTRIAL CLASSIFICATION:	INSURANCE AGENTS BROKERS & SERVICES [6411]
    		ORGANIZATION NAME:           	02 Finance
    		IRS NUMBER:				362151613
    		STATE OF INCORPORATION:			DE
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEFA14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-09761
    		FILM NUMBER:		24774438

    	BUSINESS ADDRESS:
    		STREET 1:		2850 GOLF ROAD
    		CITY:			ROLLING MEADOWS
    		STATE:			IL
    		ZIP:			60008-4050
    		BUSINESS PHONE:		630-773-3800

    	MAIL ADDRESS:
    		STREET 1:		2850 GOLF ROAD
    		CITY:			ROLLING MEADOWS
    		STATE:			IL
    		ZIP:			60008-4050

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	ARTHUR J. GALLAGHER & CO.
    		DATE OF NAME CHANGE:	20190819

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	GALLAGHER ARTHUR J & CO
    		DATE OF NAME CHANGE:	19920703
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEFA14A
    <SEQUENCE>1
    <FILENAME>no_xbrl_ajg_def_a14a_202.htm
    <DESCRIPTION>DEFA14A
    <TEXT>
    Document 1 - file: no_xbrl_ajg_def_a14a_202.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>img181189002_0.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: img181189002_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>img181189002_1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: img181189002_1.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>