Aon
Company History
Aon History: Founding, Growth & Key Milestones
Founded 1982 in Chicago, Illinois, United States
When was Aon founded?
Aon was founded in 1982 in Chicago, Illinois, United States by Patrick G. Ryan and W. Clement Stone, making it 44 years old.
- Founded
- 1982
- Founding place
- Chicago, Illinois, United States
- Founders
- Patrick G. Ryan and W. Clement Stone
- Headquarters today
- Dublin, Ireland
- Milestones documented
- 14 (1919–2025)
- Current CEO
- Greg Case
- Acquisitions
- 3
| Year | Event |
|---|---|
| 1919 | Founding of Combined Insurance by W. Clement Stone |
| 1964 | Patrick Ryan Founds Pat Ryan & Associates |
| 1982 | Historic Merger of Ryan Insurance and Combined ($500M) |
| 1987 | Adoption of the Name Aon ('Oneness') |
| 1991 | European Expansion via Hudig-Langeveldt |
| 1997 | Acquisition of Alexander & Alexander ($1.23B) |
| 2005 | Greg Case Named Chief Executive Officer |
| 2008 | Acquisition of Benfield Group ($1.75B) |
| 2010 | Acquisition of Hewitt Associates ($4.9B) |
| 2012 | Corporate Redomiciliation to London, UK |
| 2020 | Redomiciliation to Dublin, Ireland |
| 2021 | Termination of Proposed Willis Towers Watson Merger |
| 2024 | Acquisition of NFP for $13.0 Billion |
| 2025 | Revenue Reaches $13.40B with 30.2% Operating Margins |
- Where was Aon founded?
- Aon was founded in Chicago, Illinois, United States in 1982. aon.com
- Who founded Aon?
- Aon was founded by Patrick G. Ryan and W. Clement Stone.
- When did Aon start?
- Aon was founded in 1982.
- How old is Aon?
- Aon is 44 years old as of 2026.
Founding Story
The story of Aon is the confluence of two iconic 20th-century American insurance entrepreneurs: W. Clement Stone and Patrick G. Ryan. In 1919, 16-year-old W. Clement Stone founded the Combined Registry Company in Chicago with just $100 in savings, selling low-cost accident and health policies door-to-door using his famous 'Positive Mental Attitude' (PMA) philosophy. Over six decades, Combined grew into a national direct-sales insurance power. Meanwhile, in 1964, 26-year-old Patrick Ryan founded Pat Ryan & Associates in Chicago, pioneering automobile dealership finance and insurance (F&I) programs. In August 1982, Ryan engineered a historic $500 million merger between Ryan Insurance Group and Combined International, taking leadership as CEO. In 1987, Ryan rebranded the merged enterprise as Aon—the Gaelic word for 'one'—symbolizing the unification of risk and people consulting. Ryan executed an aggressive international M&A strategy, acquiring Dutch broker Hudig-Langeveldt in 1991, Britain's Bain Clarkson in 1994, and Alexander & Alexander in 1997 for $1.23 billion, surpassing Marsh to become the world's largest broker. In 2005, former McKinsey partner Greg Case was appointed CEO. Case instituted the 'Aon United' operational framework, acquired reinsurance broker Benfield Group for $1.75B in 2008, human resources titan Hewitt Associates for $4.9B in 2010, and middle-market champion NFP for $13.0B in 2024, cementing Aon's place as a global professional services titan.
Founders
Patrick G. Ryan
Patrick George Ryan (born 1937) is an American billionaire businessman and insurance visionary who founded Pat Ryan & Associates in 1964 and created Aon in 1982, serving as CEO until 2005. Ryan is an icon of the insurance industry and founder of Ryan Specialty Group.
W. Clement Stone
William Clement Stone (1902–2002) was an American businessman, author, and philanthropist who founded Combined Insurance Company in 1919 with $100. Stone was world-renowned for his Positive Mental Attitude (PMA) philosophy and bestselling personal growth books.
Key Milestones
Founding of Combined Insurance by W. Clement Stone
W. Clement Stone founds Combined Insurance in Chicago with $100, selling low-cost accident and health policies.
Source: aon.comPatrick Ryan Founds Pat Ryan & Associates
Patrick G. Ryan founds an automobile dealership finance and insurance (F&I) brokerage in Chicago.
Source: aon.comHistoric Merger of Ryan Insurance and Combined ($500M)
Patrick Ryan merges his agency with Combined International Corporation, taking leadership as CEO.
Source: aon.comAdoption of the Name Aon ('Oneness')
Rebrands the merged corporate enterprise as Aon plc, from the Gaelic word meaning 'oneness' or 'unity'.
Source: aon.comEuropean Expansion via Hudig-Langeveldt
Acquires historic Dutch insurance broker Hudig-Langeveldt, initiating aggressive European expansion.
Source: aon.comAcquisition of Alexander & Alexander ($1.23B)
Acquires premier international broker Alexander & Alexander, briefly becoming the largest insurance broker on earth.
Source: aon.comGreg Case Named Chief Executive Officer
Former McKinsey partner Greg Case appointed CEO, launching the transformative 'Aon United' strategy.
Source: aon.comAcquisition of Benfield Group ($1.75B)
Acquires British reinsurance broker Benfield Group, creating Aon Benfield, the undisputed reinsurance broking giant.
Source: aon.comAcquisition of Hewitt Associates ($4.9B)
Acquires human resources and employee benefits consulting titan Hewitt Associates, forming Aon Hewitt.
Source: aon.comCorporate Redomiciliation to London, UK
Moves corporate headquarters from Chicago to London to optimize international commercial brokerage.
Source: aon.comRedomiciliation to Dublin, Ireland
Redomiciles corporate parent to Dublin, Ireland, securing stable European Union jurisdiction post-Brexit.
Source: aon.comTermination of Proposed Willis Towers Watson Merger
Terminates proposed $30B combination with WTW following US DOJ antitrust challenges, pivoting to standalone growth.
Source: aon.comAcquisition of NFP for $13.0 Billion
Completes the landmark $13.0 billion acquisition of National Financial Partners, dramatically scaling middle-market brokerage.
Source: aon.comRevenue Reaches $13.40B with 30.2% Operating Margins
Aon reports $13.40 billion in revenue and over $4.0 billion in operating profit, generating $3.2B in free cash flow.
Source: aon.comMajor Acquisitions
National Financial Partners (NFP)
2024Hewitt Associates
2010Benfield Group
2008Keep researching Aon
Aon Company History FAQ
When was Aon founded and what does its name mean?
Aon traces its origins to 1982 when Patrick Ryan merged Ryan Insurance Group with W. Clement Stone's Combined International Corporation. In 1987, the merged entity rebranded as Aon, which is a Gaelic word meaning 'one', symbolizing unity and integrated global risk capabilities.
Why did Aon relocate its corporate headquarters to London and Dublin?
Aon moved its corporate headquarters from Chicago to London in 2012 to establish closer proximity to Lloyd's of London and international insurance capital markets. In 2020, Aon subsequently shifted its corporate domicile to Dublin, Ireland, taking advantage of European corporate structures and stability.
What happened to Aon's proposed merger with Willis Towers Watson?
In March 2020, Aon agreed to acquire Willis Towers Watson in a $30 billion all-stock mega-merger. However, after extensive antitrust opposition from the United States Department of Justice regarding market concentration in commercial broking and reinsurance, both firms terminated the transaction in July 2021.
How did Patrick Ryan and W. Clement Stone merge their distinct businesses in 1982?
Patrick Ryan recognized that combining Pat Ryan & Associates' corporate dealership brokerage with Combined's consumer health and life agency would create a scaled national powerhouse, leading to the 1982 merger and 1987 rebranding to Aon.
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