Marsh McLennan

Marsh & McLennan Companies, Inc., trading as Marsh McLennan and Marsh, is an American professional services firm headquartered in New York City, with businesses in insurance brokerage, risk management, reinsurance services, talent management, investment advisory, and management consulting. Its four main operating companies are Marsh (54% of 2025 revenues), which offers risk management, insurance broking, insurance program management, risk consulting, analytical modeling, and alternative risk financing services; Marsh Re (formerly Guy Carpenter; 10% of 2025 revenues), a reinsurance intermediary and advisor; Mercer (23% of 2025 revenues), which provides consulting to employers for health insurance, retirement plans, and pension plans; and Oliver Wyman (13% of 2025 revenues), including Lippincott and NERA Economic Consulting, which provides consulting services. In 2024, risk and insurance services contributed a total of 63% of revenues and 71% of operating profit, while consulting contributed 37% of revenues and 29% of operating profit. It is the largest insurance broker worldwide. The company is ranked 175th on the Fortune 500 and 267th on the Forbes Global 2000.