Aon plc is a global professional services firm that offers a range of risk-mitigation products. Aon has approximately 50,000 employees across 120 countries. Founded in Chicago by Patrick Ryan, Aon was created in 1982 when the Ryan Insurance Group merged with the Combined Insurance Company of America under W. Clement Stone. In 1987, the holding company was renamed Aon from aon, a Gaelic word meaning "one". The company is globally headquartered in London with its North America operations based in Chicago at the Aon Center. Aon is listed on the New York Stock Exchange under AON with a market cap of $65 billion in April 2023. Wikipedia