Who is the biggest reinsurance broker in the world?

Aon Reinsurance Solutions Takes the Lead in 2025

When it comes to reinsurance brokerage, one name stands at the top of the pack in 2025: Aon Reinsurance Solutions. With reported revenues of $2.656 billion in 2024, Aon has secured its position as the world’s largest reinsurance broker—edging out its closest competitor, Guy Carpenter, which recorded $2.544 billion for the same period.

The reinsurance brokerage landscape has long been dominated by a tight cluster of global players, but Aon’s consistent performance and strategic focus on integrated risk solutions have given it a decisive edge. Their global reach, combined with deep analytics and client-centric advisory services, has attracted major insurers looking for sophisticated risk transfer strategies in an era of increasing volatility—from climate events to evolving cyber threats.

While Guy Carpenter, a subsidiary of Marsh & McLennan, maintains strong momentum, and Gallagher Re continues to grow with a diversified portfolio, the gap between first and second place remains narrow. Meanwhile, firms like Howden Re are climbing fast, reporting $689 million in revenue, signaling increasing competition in a market that values agility and innovation.

What sets Aon apart isn’t just scale—it’s the ability to blend reinsurance expertise with broader risk management services. In a world where insurers demand more than just placement power, Aon’s holistic approach has proven compelling.

As the full-year rankings for 2025 confirm, the reinsurance brokerage space is as competitive as ever. But for now, Aon Reinsurance Solutions wears the crown, setting the pace in a high-stakes, rapidly evolving industry.