X0609 4 2026-09-02 0000354190 Arthur J. Gallagher & Co. AJG 0001482241 Hudson Scott R false 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 Vice President 0 Common Stock 2026-09-02 4 M 0 12000 86.17 A 102262 D Common Stock 2026-09-02 4 S 0 12000 264.133 D 90262 D Common Stock 411.467 I Gallagher 401(k) plan account Non-qualified Stock Option 86.17 2026-09-02 4 M 0 12000 0 D 2027-03-12 Common Stock 12000 12370 D Non-qualified Stock Option 127.90 2028-03-16 Common Stock 23025 23025 D Non-qualified Stock Option 228.20 2033-03-01 Common Stock 15800 15800 D Non-qualified Stock Option 158.56 2029-03-15 Common Stock 11480 11480 D Non-qualified Stock Option 337.74 2032-03-01 Common Stock 10579 10579 D Non-qualified Stock Option 243.54 2031-03-01 Common Stock 10047 10047 D Phantom Stock Common Stock 3717.894 3717.894 D Notional Stock Units Common Stock 4134.7414 4134.7414 D Non-qualified Stock Option 177.09 2030-03-15 Common Stock 9558 9558 D The price reported is an average weighted price. The shares were sold in multiple transactions on 9/2/2026 at prices ranging from $263.894 to $264.15. The reporting person will provide to the Securities and Exchange Commission staff, the issuer, or any security holder of the issuer, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in the footnotes to this Form 4. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Closing price of Gallagher common stock on February 28, 2025. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Each share of phantom stock represents a right to receive one share of Gallagher common stock. 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 when they attain age 62, or after a one-year period for participants who have attained age 61. Each notional stock unit represents a right to receive one share of Gallagher common stock. The notional stock units become payable in July 2026 and following the reporting person's separation from service with Gallagher. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. /s/ Monica Norzagaray, by power of attorney 2026-09-04