Marsh & McLennan Companies, Inc. is a global professional services firm, headquartered in New York City with businesses in insurance brokerage, risk management, reinsurance services, talent management, investment advisory, and management consulting.[3] Its four main operating companies are Guy Carpenter, Marsh, Mercer, and Oliver Wyman Group.[4]

Marsh & McLennan Companies ranked #212 on the 2018 Fortune 500 ranking, the company's 24th year on the annual Fortune list,[5] and #458 on the 2017 Forbes Global 2000 List.[6]

Marsh & McLennan's 2016 revenue of $13.2 billion ranked it #1 on Business Insurance's ranking of the world's largest insurance brokers.