The largest reinsurance brokers globally are massive multinational risk-advisory powerhouses that dominate global treaty placements. Guy Carpenter (a subsidiary of Marsh & McLennan Companies) and Aon Benfield (the reinsurance division of Aon plc) stand as the two undisputed global giants in the reinsurance brokerage sector, alongside Willis Re (now part of Arthur J. Gallagher & Co.), managing massive volumes of global risk capital flows.