Aon plc stands as one of the world’s leading professional services firms, with a broad global footprint (over 120 countries and more than 65,000 colleagues). Renowned for its risk management and human capital solutions, Aon serves clients in areas spanning commercial insurance brokerage, reinsurance intermediation, employee benefits, retirement planning, and HR advisory. In 2025, Aon’s business is organized into five key segments: Commercial Risk Solutions, Reinsurance Solutions, Health & Benefits Consulting, Retirement & Wealth Solutions, and Human Capital Advisory. Through these units, Aon delivers services ranging from corporate risk transfer and insurance broking, to reinsurance placement for insurers, to consulting on health benefits and wellbeing programs, pension plan management and investments, as well as workforce talent and compensation strategy.
Aon’s global market presence is formidable – it is routinely ranked among the top two insurance brokers worldwide by revenue. For instance, in 2024 Aon generated approximately $15.7 billion in revenue (up 17% year-on-year, including 6% organic growth), reflecting strong client demand across all regions.
The firm’s Commercial Risk Solutions arm helps businesses manage property, liability, and specialty risks; Reinsurance Solutions advises insurance companies on capital and catastrophe protection; Health & Benefits consulting supports employers in optimizing health insurance and wellness benefits for their workforce; Retirement & Wealth Solutions provides actuarial and investment advice for pension funds and wealth management; and Human Capital Advisory covers broader talent, compensation, and HR strategy consulting.
This diversified portfolio has enabled Aon to build resilient growth. Notably, Aon has emphasized new innovation areas – from leveraging data analytics and AI for risk insights, to developing solutions for climate change risks and evolving healthcare needs – to stay ahead in a changing risk landscape.
However, Aon faces intense competition on all fronts. Its major global rivals include multi-line insurance brokers and consultants like Marsh McLennan and Willis Towers Watson (WTW), specialist brokerage firms like Arthur J. Gallagher & Co., leading reinsurers such as Munich Re and Swiss Re, and human capital consultants like Mercer, among others. These competitors are themselves industry giants with significant resources, and they compete with Aon across its segments – in commercial risk brokerage, reinsurance, employee benefits, retirement solutions, and HR advisory. Below, we profile Aon’s top global competitors , examining their recent financial performance, strategic moves (including acquisitions and innovations), and key areas of market overlap with Aon’s businesses. Each competitor brings a unique mix of strengths, and together they highlight the dynamic, highly competitive environment in which Aon operates.
Top Competitors of Aon
1. Marsh McLennan (Marsh & McLennan Companies)
Website – https://www.marshmclennan.com/
Marsh McLennan (NYSE: MMC) stands as the world’s largest professional services firm, operating across four powerful divisions—Marsh, Guy Carpenter, Mercer, and Oliver Wyman—that directly mirror Aon’s offerings. The company dominates the global insurance broking, reinsurance, and consulting landscape, with over 90,000 employees and $24.3 billion in 2024 revenue, marking its 17th straight year of margin expansion. Under CEO John Doyle, 2024 was a landmark year characterized by strong 8% revenue growth, robust acquisitions, and a record-breaking $7.75 billion purchase of McGriff Insurance Services, solidifying Marsh’s U.S. middle-market presence. The firm’s financial momentum carried into 2025, with double-digit revenue gains and continued leadership in both its insurance and consulting segments.
Strategically, Marsh McLennan’s expansion is powered by 48 acquisitions in 2024, aggressive technological innovation, and a focus on sustainability. Its AI-driven platform Sentrisk, developed by Marsh and Oliver Wyman, helps clients manage supply chain risks through machine learning and satellite data, underscoring its commitment to advanced analytics. The firm’s Climate and Sustainability practice further positions it as a leader in climate risk advisory. As Aon’s most formidable global rival, Marsh McLennan competes across every major service area—from commercial and reinsurance broking to human capital and strategic consulting. The rivalry is particularly fierce in global insurance brokerage, where Marsh retains the #1 spot worldwide, consistently edging out Aon in scale, client reach, and market influence.
2. Willis Towers Watson (WTW)
Website – https://www.wtwco.com/en-in
Willis Towers Watson (NASDAQ: WTW) is a global leader in insurance broking and advisory services, operating through two core segments—Risk & Broking and Health, Wealth & Career—that closely mirror Aon’s business model. Formed from the 2016 merger of Willis Group and Towers Watson, WTW serves clients in over 140 countries with 46,000 employees. After its blocked $30 billion merger attempt with Aon, WTW refocused on independent growth and specialization. In 2024, the company generated $9.93 billion in revenue, up 5% year-over-year, led by solid organic growth and strong performances in corporate insurance and specialty lines such as marine and facultative reinsurance. Despite one-time impairment charges from selling Tranzact, WTW’s core operations strengthened, and by mid-2025, it maintained 5% organic growth while expanding margins. CEO Carl Hess emphasized efficiency gains, strategic share repurchases, and completion of a transformation program that delivered $473 million in cost savings.
Strategically, WTW has sharpened its competitive edge through targeted expansion, technology innovation, and re-entry into reinsurance. In 2025, it launched a joint venture with Bain Capital to rebuild its reinsurance brokerage presence, signaling renewed competition with Aon and Gallagher. Its “specialization strategy” focuses on niche expertise in areas like aerospace, surety, and financial lines, fueling double-digit growth across key regions. The firm is also pioneering AI and analytics-driven solutions—integrating generative AI into its RiskAgility modeling platform, launching Radar Vision for real-time insurance insights, and embedding AI coaching in its Engage employee experience platform. These innovations echo Aon’s tech-forward approach. With strong overlap in insurance, benefits, retirement, and human capital consulting, WTW remains one of Aon’s closest global rivals, competing head-to-head in client accounts, data-driven tools, and climate risk advisory, ensuring a fiercely contested landscape through 2025.
3. Arthur J. Gallagher & Co. (Gallagher)
Website – https://www.ajg.com/
Gallagher (NYSE: AJG) has rapidly transformed from a U.S.-centric middle-market broker into a top-three global insurance powerhouse, competing head-on with Aon and Marsh. Operating through its Brokerage and Risk Management segments, the firm now spans 130+ countries and generated $11.4 billion in 2024 revenue, up 15% year-on-year. Strong organic growth (~10%) and an aggressive acquisition strategy have fueled this rise, highlighted by the 2021 Willis Re acquisition, which made Gallagher Re a major reinsurance intermediary. In 2024 alone, Gallagher completed 48 acquisitions and achieved record profitability, with $1.47 billion in net earnings, up 52% from 2023. Its 2025 momentum has continued with double-digit growth in both revenue and earnings, supported by scale efficiencies and a consistent streak of 16 consecutive quarters of double-digit organic growth—a testament to disciplined execution and expanding global influence.
Strategically, Gallagher’s strength lies in acquisition-driven expansion, industry specialization, and a quiet but steady push into data analytics and innovation. Its $2.9 billion acquisition of AssuredPartners (announced in late 2024) is poised to dramatically increase U.S. brokerage scale and could bring Gallagher’s pro-forma revenues close to Aon’s. Gallagher Re has also become a formidable competitor in reinsurance, growing ~30% annually and ranking #3 worldwide, while offering advanced catastrophe modeling and climate-risk advisory akin to Aon’s tools. The company’s client-centric philosophy and focus on specialty sectors like cyber, public sector, and captives give it a differentiated edge. Although less vocal about technology than peers, Gallagher is enhancing its analytics, publishing AI-driven market reports and developing benchmarking tools to optimize insurance programs. Today, Gallagher’s expanding reach, reinsurance strength, and strong financial trajectory position it as Aon’s fastest-rising rival, intensifying competition across global commercial risk, reinsurance, and benefits consulting.
4. Munich Re (Munich Reinsurance Company)
Website – https://www.munichre.com/en.html
Munich Re stands apart from traditional brokers like Aon as the world’s largest reinsurance company and a powerful primary insurer through its ERGO subsidiary. While Aon acts as an intermediary, Munich Re is a risk carrier, directly assuming insurance and reinsurance risks on its balance sheet. This gives it enormous influence over the global risk ecosystem. With around 44,000 employees, it dominates reinsurance markets, sets pricing trends, and provides advisory and analytical services that sometimes overlap with Aon’s. In 2024, it generated €60.8 billion in insurance revenue and €5.7 billion net profit, reflecting a strong 14% ROE. Favorable pricing and disciplined underwriting helped it outperform peers, and by mid-2025, its net profit had already reached €3.2 billion, putting it on track to meet its €6 billion target. Its financial strength and diversification give it a strategic edge, allowing it to absorb mega-loss events and maintain stability in volatile markets.
Strategically, Munich Re is evolving into a “risk solutions” leader, driving innovation in climate resilience, AI, and new risk frontiers. It actively develops risk models and bespoke coverages for complex emerging threats — from climate-exacerbated catastrophes to cyber, renewable energy, and AI-related exposures — and has committed to net-zero by 2050. Its deep climate research, NatCatSERVICE database, and advanced analytics directly compete with Aon’s impact forecasting tools. Through Munich Re Ventures, it invests in insurtech and climate-tech, reinforcing its innovation pipeline. The firm often partners with Aon, as Aon brokers billions in reinsurance placements to Munich Re, but also competes indirectly by offering direct risk transfer, advisory services, and capital market solutions that can bypass brokers. In short, Munich Re is both a critical partner and a formidable competitor, leveraging its balance sheet strength, data leadership, and climate expertise to shape the global risk landscape in ways that challenge Aon’s advisory dominance.
5. Swiss Re
Website – https://www.swissre.com/
Swiss Re, the world’s second-largest reinsurer, is a major force in the global risk ecosystem and a significant indirect competitor to Aon. Headquartered in Zurich with around 14,000 employees, Swiss Re operates through Property & Casualty Reinsurance, Life & Health Reinsurance, Corporate Solutions, and Admin Re. Unlike brokers, it assumes risk directly, but overlaps with Aon through its advisory services, analytics, and product innovation. In 2024, Swiss Re delivered $3.2 billion in net income and a 15% ROE, with strong underwriting, improved life and health results, and rising investment income. By mid-2025, net income hit $2.6 billion (ROE 23%), positioning the company well to meet its ambitious $4.4 billion 2025 profit target. Its Corporate Solutions unit is becoming increasingly profitable, offering specialty insurance directly to corporates—an area that can bypass brokers. With an S&P AA- credit rating and disciplined pricing, Swiss Re’s financial strength and market influence play a critical role in shaping reinsurance availability and pricing for Aon’s clients.
Strategically, Swiss Re is advancing in climate resilience, parametric insurance, AI, and digital distribution. It has taken bold ESG steps, reducing carbon exposure while expanding insurance for renewables and climate adaptation. Innovations like parametric hail and weather covers, its white-label digital insurance platform iptiQ, and proprietary AI-powered underwriting models reflect its shift toward becoming a solutions provider, not just a reinsurer. Swiss Re’s Sigma reports and risk modelling capabilities rival Aon’s analytics, and its Capital Partners unit competes with Aon’s capital advisory in connecting insurers to ILS markets. While Swiss Re often partners with Aon as a key capacity provider, it also competes by offering direct placements, bypassing brokers, and influencing risk strategies through its intellectual leadership. Its growing role in digital insurance ecosystems and climate-centric solutions underscores its evolution into a powerful partner–competitor hybrid, compelling Aon to continuously prove the added value of its independent advisory model.
6. Mercer (Marsh McLennan’s Mercer)
Website – https://www.mercer.com/en-in/
Mercer, a subsidiary of Marsh McLennan, is one of the world’s leading HR, health, and investment advisory firms, and a core competitor to Aon in the human capital and benefits consulting space. It specializes in Health & Benefits, Wealth & Retirement, and Career/Workforce solutions, serving Fortune 500 clients in over 40 countries. Historically a key rival to Aon Hewitt, Mercer continues to compete fiercely in areas like retirement plan de-risking, health cost containment, and workforce transformation. In 2024, Mercer generated $5.74 billion in revenue, growing 5% organically, with especially strong momentum in its health and investment businesses. Its Wealth segment benefited from volatile markets driving demand for investment advisory, while Career consulting grew steadily as employers revamped talent strategies amid tight labor markets. By early 2025, Mercer remained on a stable mid-single-digit growth path, driven by strong client retention and new wins, mirroring Aon’s performance in this segment.
Mercer’s competitive strength comes from a series of strategic acquisitions between 2023–2025. It bought Leapgen to strengthen digital HR transformation capabilities, acquired Vanguard’s OCIO business (adding $130B AUA) to dominate delegated investment management in the U.S., and took over Cardano’s pension consulting units in the UK and Netherlands to boost its European pension presence. In early 2025, it added SECOR Asset Management to enhance its institutional investment advisory. These moves underscore Mercer’s aggressive scaling in health tech, OCIO, and pension risk — areas where Aon also plays strongly. Beyond acquisitions, Mercer has doubled down on innovation, deploying digital tools like Mercer Benefits Central and Mercer Marketplace for benefits administration, Mercer Insights for investment analytics, and AI-driven workforce analytics to support talent and pay equity strategies. Its ESG leadership, particularly in sustainable investing for pension portfolios, further strengthens its advisory brand.
The overlap with Aon is extensive. In health & benefits, Mercer and Aon are the top two global consultants, competing directly for large corporate RFPs on plan design, cost management, and global harmonization. In retirement & wealth, both advise on defined benefit plan de-risking, funding strategies, and investment consulting — though Mercer’s OCIO acquisitions may give it a scale edge. In human capital advisory, Mercer’s Career business — known for its compensation surveys, workforce analytics, and executive pay consulting — mirrors Aon’s talent and rewards offerings. Both also compete in HR tech transformation, with Mercer leveraging Leapgen’s expertise while Aon leans on its analytics and advisory heritage. They operate in nearly identical geographic markets (U.S., U.K., Europe, Asia, LATAM), often going head-to-head for the same clients.
Finally, Mercer matches Aon’s technological investments. Platforms like Mercer’s Thomsons (Darwin) directly rival Aon’s benefits administration tools, while Mercer’s AI and analytics focus parallels Aon’s workforce and risk intelligence initiatives. Both firms are shaping solutions around the same mega-trends — aging populations and pension reform, telehealth and mental health in benefits, ESG integration, and AI in HR. Mercer’s integration with Marsh McLennan also gives it added distribution power, similar to Aon’s own unified strategy across its business lines. In short, Mercer remains Aon’s closest and most balanced rival in health, wealth, and human capital consulting, pushing both firms to continuously innovate, acquire capabilities, and differentiate their value propositions in an intensely competitive global advisory market.
Other Notable Competitors: Lockton and Howden
Beyond the giants above, Aon also faces growing competition from independent brokerage firms that are expanding globally. Two prominent examples are Lockton and Howden Group, which, while smaller than Aon, are making significant strides in one or more of Aon’s arenas.
Lockton:
Lockton, headquartered in the U.S., is the world’s largest privately held insurance brokerage and a rapidly growing challenger to Aon in commercial risk and employee benefits advisory. For the fiscal year ending April 2025, Lockton reported $4.0 billion in revenue, up 13% year-over-year, marking its fifth consecutive year of double-digit organic growth. Operating in 125+ countries with 13,000 employees, Lockton has built its expansion on organic reinvestment in talent and market growth rather than large acquisitions. A key strategic pillar has been Lockton Re, its reinsurance brokerage arm launched in 2018. In just five years, Lockton Re grew to 22 offices globally and 300+ insurer clients, achieving 29% revenue growth in 2024, making it a credible alternative to Aon’s reinsurance solutions for mid-sized insurers.
Lockton is also evolving toward a broker-consultant model, mirroring Aon’s integrated strategy. It established a Data, Analytics & Digital Office to enhance its use of AI and data insights for smarter risk advisory. In employee benefits, it competes head-to-head with Aon in the mid-market through health, benefits, and wellbeing consulting, often leveraging its independence as a selling point to offer more flexible service and pricing. Its Benefits Benchmarking Survey and consulting capabilities closely resemble Aon’s offerings. With its client-first culture, rising global presence, and aggressive growth trajectory, Lockton is increasingly a serious competitive force in commercial risk broking across North America, Europe, and Asia-Pacific — and a growing disruptor in both reinsurance and benefits consulting.
Howden Group:
Howden Group Holdings, headquartered in London, has quickly emerged as a top-5 global insurance intermediary, competing head-to-head with larger players like Aon. In FY 2024, Howden reported £3.01 billion in revenue (≈$3.7–4 billion), up 23% year-over-year with 15% organic growth. A key accelerator was its 2022 acquisition of TigerRisk Partners for $1.6 billion, which propelled Howden Re into major reinsurance markets in the U.S. and Bermuda, enabling it to challenge Aon in reinsurance placements. Its reinsurance arm grew 30% in 2024, and overall scale now matches Lockton. Howden’s strategy blends M&A with aggressive talent acquisition, often hiring senior teams from Marsh, Aon, and WTW — moves that have sparked multiple legal battles. With acquisitions like Aston Lark in the UK and a 2025 launch of its U.S. retail brokerage arm, Howden is expanding its geographic and segment reach, bringing direct competition to Aon’s home turf.
Strategically, Howden positions itself as an employee-owned, client-focused alternative to publicly listed brokers, mirroring Lockton’s culture. Its capabilities span retail brokerage, Lloyd’s market placement, reinsurance broking, and increasingly specialty and capital market solutions through Howden Capital Markets. The firm is also making strides in innovation and climate risk, launching products like parametric hurricane covers for the Caribbean and expanding its renewable energy insurance offerings. Though smaller than Aon, Howden’s rapid growth trajectory, global expansion, and deepening specialty expertise make it a serious competitor. Aon now faces Howden not only in reinsurance (Howden Re approaching $600 million in revenue) but also in corporate insurance and specialty placements, especially in Europe and Asia. As Howden chips away at market share through nimble operations and talent-driven expansion, Aon must defend its position by reinforcing its scale advantages and global-local service proposition.
Conclusion
The competitive landscape for Aon in 2025 is intense and continually evolving. Aon’s top global competitors – from multi-line giants like Marsh McLennan and WTW, to the ascendant Gallagher, the powerhouse reinsurers Munich Re and Swiss Re, the specialist Mercer, and fast-growing brokers like Lockton and Howden – each bring formidable strengths. They challenge Aon across all its solution lines: battling for insurance brokerage dominance, innovating in reinsurance and capital solutions, advising on health and retirement amid demographic and technological shifts, and harnessing AI and analytics to deliver insights to clients. Many of these competitors have made bold moves recently: Marsh McLennan with transformative acquisitions and AI platforms, WTW with a renewed focus and tech investments, Gallagher with unprecedented expansion via M&A, and Mercer with targeted acquisitions to deepen capabilities. Simultaneously, reinsurers are pushing the envelope on product innovation and climate risk management, while independents like Lockton and Howden grow at extraordinary rates by capitalizing on client and talent discontent with the status quo.
For Aon, maintaining its leadership position will require leveraging its unified model – the “Aon United” approach – to provide integrated risk and human capital solutions that differentiate from the pack. Aon continues to invest in its own innovation (for example, its partnerships in analytics and development of climate resilience tools) to stay ahead. The firm’s global scale and breadth across risk and people solutions remain key competitive advantages, but the profiles above show that rivals are closing some gaps through strategic moves. In areas like AI in insurance and climate risk solutions, competition is as much about thought leadership and technology as it is about market share – Aon and its competitors are racing to offer the most advanced advisory services. Likewise, in health and wealth, firms like Mercer and WTW ensure Aon cannot rest on past laurels, driving constant enhancement of offerings (such as new health analytics or innovative retirement plan designs).
Ultimately, Aon’s market is characterized by both consolidation at the top and disruption from ambitious newer entrants. Clients benefit from this vigorous competition through more choice and innovation. Aon, with its rich legacy, global reach, and diversified expertise, remains a front-runner – but as this 2025 competitive overview illustrates, it is a race with no finish line. Each major competitor profiled is vying to shape the future of risk management and human capital solutions, compelling Aon to continuously adapt, innovate, and prove its value in a crowded global arena.
Also Read: Who are AXA’s Top Competitors in Global Insurance Industry?
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