| AonDublin-domiciled global broker with 2025 revenue of $17.2 billion across commercial risk, reinsurance, health and retirement; owns the NFP benefits arm. | Global brokers | Dublin, Ireland | $17,181 million (2025 Form 10-K and Jan. 30, 2026 results release) |
| Arthur J. Gallagher & Co.Illinois-based global broker founded in 1927, with 2025 revenue of $13.8 billion and a bigger U.S. middle-market arm after buying AssuredPartners in 2025. | Global brokers | Rolling Meadows, Illinois | $13,778 million before reimbursements; $13,942 million total (Jan. 29, 2026 results release) |
| LocktonKansas City, Missouri broker, privately held and family-owned since 1966, ranked No. 8 worldwide by 2025 brokerage revenue of $4.37 billion. | Global brokers | Kansas City, Missouri | $4.37 billion brokerage revenue, 2025 (Business Insurance ranking, June 26, 2026); $4.0 billion global revenue for the fiscal year ended April 30, 2025 (Lockton release, June 16, 2025) |
| Marsh McLennanThe largest insurance broker by revenue, now branded Marsh, with Guy Carpenter, Mercer, Oliver Wyman and the U.S. middle-market arm Marsh McLennan Agency. | Global brokers | New York, New York | $26,981 million (2025 results release, Jan. 29, 2026) |
| WTWLondon-based global broker and consultancy formed by the 2016 Willis-Towers Watson merger, with 2025 revenue of $9.7 billion and a 2026 U.S. push via Newfront. | Global brokers | London, England | $9,708 million (2025 Form 10-K and Feb. 2026 results release) |