Top 5 Insurance Brokers in the UK (2023 Revenue Rankings)

By 2023 global revenue (£ billions):

1. Marsh McLennan – £17.2B (Marsh, Guy Carpenter, Mercer, Oliver Wyman)
2. Aon – £11.1B (Commercial Risk, Reinsurance, Health, Retirement)
3. Willis Towers Watson – £8.2B (Risk & Broking, Health/Wealth, Talent)
4. Arthur J. Gallagher – £7.3B (Risk Mgmt, Benefits, Specialty, Reinsurance)
5. Lockton – £2.1B (Privately held; Commercial, Benefits, Specialty)

Rankings shift annually; "best" depends on client size, sector, and service needs.