The United States insurance brokerage market features several massive multinational corporations that manage complex commercial risk portfolios, employee benefits, and reinsurance placements. The top industry leaders include Marsh & McLennan Companies, Aon, and Willis Towers Watson, which collectively dominate global corporate brokerage. Other prominent brokerage and advisory firms operating at massive scales across North America include Arthur J. Gallagher & Co., Hub International, Truist Insurance Holdings, and Alliant Insurance Services, serving corporate clients worldwide.