Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Bay Walter D. 2. Issuer Name and Ticker or Trading Symbol Arthur J. Gallagher & Co. [AJG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) General Counsel (Last) (First) (Middle) 2850 GOLF ROAD 3. Date of Earliest Transaction (Month/Day/Year) 12/19/2025 (Street) ROLLING MEADOWS, IL 60008-4002 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 12/19/2025 M 15,850 A $79.59 95,399 D Common Stock 12/19/2025 S 15,850 D $255 79,549 D Common Stock 12/19/2025 G 1,724 D $ 0 77,825 D Common Stock 418.689 I Gallagher 401(k) plan account

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Underlying Securities (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Phantom Stock	(1)							(2)	(2)	Common Stock	3,395.152		3,395.152	D
Non-qualified Stock Option	$86.17							(3)	03/12/2027	Common Stock	17,630		17,630	D
Non-qualified Stock Option	$127.9							(3)	03/16/2028	Common Stock	24,500		24,500	D
Non-qualified Stock Option	$158.56							(3)	03/15/2029	Common Stock	11,405		11,405	D
Non-qualified Stock Option	$177.09							(4)	03/15/2030	Common Stock	9,452		9,452	D
Non-qualified Stock Option	$243.54							(5)	03/01/2031	Common Stock	10,884		10,884	D
Non-qualified Stock Option	$337.74(6)							(3)	03/01/2032	Common Stock	11,350		11,350	D
Notional Stock Units	$ 0 (7)							(8)	(8)	Common Stock	5,228.41		5,228.41	D
Non-qualified Stock Option	$79.59	12/19/2025		M			15,850	(3)	03/14/2026	Common Stock	15,850	$ 0	0	D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Bay Walter D. 2850 GOLF ROAD ROLLING MEADOWS, IL 60008-4002			General Counsel

Signatures

/s/ Monica Norzagaray, by power of attorney		12/23/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Each share of phantom stock represents a right to receive one share of Gallagher common stock.
(2)	These shares represent awards under the Age 62 Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the reporting person. Participants vest in these awards in the year they attain age 62, or after a one-year period for participants who have attained age 61.
(3)	One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date.
(4)	One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date.
(5)	One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date.
(6)	Closing price of Gallagher common stock on February 28, 2025.
(7)	Each notional stock unit represents a right to receive one share of Gallagher common stock.
(8)	The notional stock units become payable following the reporting person's separation from service with Gallagher.
Remarks: Exhibit List: Ex-24: Power of Attorney.

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