Aon plc
Aon plc (AON)
Overview
Aon is one of the world's largest professional services firms in risk, insurance brokerage, reinsurance, health, and retirement/wealth advisory. Incorporated in Ireland with global operational headquarters in London (and major North American operations based in Chicago), Aon serves clients in more than 120 countries through tens of thousands of employees ("colleagues," in company parlance). The firm generated total revenue of $17.2 billion in fiscal year 2025, up 9% from $15.7 billion in 2024, aided by 6% organic growth and the continued integration of its landmark NFP acquisition. Aon is generally regarded as the second-largest insurance broker in the world by revenue, behind Marsh McLennan.
What They Do & How They Make Money
Aon does not underwrite insurance risk itself; instead, it acts as an intermediary and advisor, earning revenue primarily through commissions and fees paid for placing insurance and reinsurance coverage on behalf of corporate, institutional, and (increasingly, via NFP) middle-market and individual clients, plus fees for a broad range of consulting and advisory services. On the brokerage side, Aon helps organizations identify, quantify, and transfer risk — negotiating property, casualty, liability, executive, and specialty insurance policies with insurance carriers, and, on the reinsurance side, helping insurance companies themselves transfer portions of their risk to reinsurers. On the advisory side, Aon earns consulting fees for services like employee health and benefits plan design and administration, retirement plan and pension consulting, actuarial services, executive compensation and talent advisory, and data-driven risk analytics. A growing share of revenue also comes from proprietary data, analytics, and technology platforms that Aon has built (and acquired) to help clients model catastrophe risk, cyber risk, and other complex exposures — an area the company has emphasized as central to its "Aon United" strategy of cross-selling integrated risk, retirement, and health solutions to clients. The 2024 completion of its ~$13.4 billion acquisition of NFP, a middle-market insurance brokerage and benefits/wealth advisory firm, significantly expanded Aon's presence in the small-and-mid-size business segment, complementing its traditional large-enterprise client base.
Business Segments
Aon reports four operating segments:
- Commercial Risk Solutions (largest segment, $8.5 billion in 2025 revenue, +8%): Core property & casualty insurance brokerage, risk consulting, and specialty insurance placement for businesses of all sizes, including the newly integrated NFP middle-market operations.
- Reinsurance Solutions ($2.8 billion, +5%): Advisory and broking services that help insurance and reinsurance companies transfer catastrophe and other risk, plus capital markets and insurance-linked securities services.
- Health Solutions ($3.8 billion, +15% — the fastest-growing segment): Employee health and benefits consulting, health insurance brokerage, and related advisory services for employers.
- Wealth Solutions ($2.1 billion, +10%): Retirement, pension, and investment consulting, actuarial services, and (prior to a 2025 divestiture) wealth advisory — Aon recorded a $1.2 billion gain in 2025 from the sale of its NFP Wealth business as part of ongoing portfolio optimization.
At a higher level, Aon groups these into two broader pillars: "Risk Capital" (Commercial Risk and Reinsurance, historically about two-thirds of revenue) and "Human Capital" (Health and Wealth, roughly one-third), reflecting the company's strategic emphasis on connecting risk and human-capital advice for clients.
Competitors
- Marsh McLennan: Aon's largest and most direct global competitor, similarly spanning insurance brokerage (Marsh), reinsurance (Guy Carpenter), and consulting (Mercer, Oliver Wyman).
- Willis Towers Watson (WTW): A close global peer competing across insurance brokerage, reinsurance, and human capital consulting; Aon and WTW attempted (and abandoned, in 2021) a ~$30 billion merger due to antitrust concerns.
- Arthur J. Gallagher & Co.: A fast-growing competitor in commercial insurance brokerage and risk management, particularly active in middle-market and specialty niches.
- Brown & Brown: A growing competitor in insurance brokerage, especially in the U.S. middle market.
- Lockton: The largest privately held independent insurance broker, competing directly for commercial and specialty accounts.
- Guy Carpenter (Marsh McLennan) and TigerRisk/Howden Re: Direct competitors in reinsurance broking.
Competitive Position
Aon's competitive advantages stem from its scale and global reach, deep specialty and industry expertise (particularly in areas like cyber risk, catastrophe modeling, and executive risk), proprietary data and analytics capabilities that are difficult for smaller brokers to replicate, and long-standing client relationships built on advisory trust rather than one-off transactions. Insurance brokerage is a relationship- and expertise-driven business with meaningful barriers to entry at the large-enterprise and specialty end of the market, and Aon's breadth across risk, health, and wealth lets it cross-sell services and offer integrated solutions that smaller, single-line competitors cannot match. The NFP acquisition also gives Aon a stronger foothold in the fragmented, high-growth middle-market segment, which had historically been a relative weak spot compared to Marsh McLennan and Gallagher.
Principal risks include intense competition from Marsh McLennan and other large brokers on both price and talent, exposure to insurance market cycles (a "soft" pricing market can compress commission-based revenue growth), integration and leverage risk from the debt-financed NFP deal, regulatory and antitrust scrutiny of large brokerage consolidation, and reputational/E&O liability risk inherent to advisory and fiduciary services. As with peers, Aon must also continue investing in technology and analytics to defend its advisory value proposition against both larger rivals and smaller, more nimble specialty brokers and insurtechs.