X0508 4 2025-02-27 0000354190 Arthur J. Gallagher & Co. AJG 0001929606 Gallagher Patrick Murphy 2850 GOLF ROAD ROLLING MEADOWS IL 60008 1 Chief Operating Officer 0 Common Stock 2025-02-27 4 M 0 5250 70.74 A 45557.8567 D Common Stock 2025-02-27 4 S 0 2613 332.518 D 42944.8567 D Common Stock 10120 I By Spouse as Trustee Common Stock 367.549 I Gallagher 401(k) plan account Common Stock 7964 I By Spouse's Trust Common Stock 80891 I By Trust Common Stock 20032 I By Trust Common Stock 54859 I By Irrevocable Trust Non-qualified Stock Option 70.74 2025-02-27 4 M 0 5250 0 D 2025-03-15 Common Stock 5250 0 D The price reported is an average weighted price. The shares were sold in multiple transactions at prices ranging from $332.476 to $332.555. 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 range set forth in this footnote. Shares held in trusts, for the benefit of the reporting person's children, of which his wife is sole trustee. Shares held in revocable trust of which the reporting person's spouse is sole Trustee and as to which he disclaims beneficial ownership. Shares held in trust for the benefit of the reporting person's children, of which he is a trustee. Shares held in trust for the benefit of the reporting person's children, of which he is a trustee. Grant date of 3/15/2018. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. /s/ Ryan Session, by power of attorney 2025-02-28