During his time at Aon, O’Halleron has led Aon's reinsurance division from its inception in 1987, and held several senior operating positions.
He will remain in his current role until 1 May and will then offer strategic counsel to the firm on an ongoing basis.
Greg Case, president and CEO of Aon, commented: “Mike O’Halleran leaves a lasting legacy as a founder, business builder, client advisor and mentor at Aon. He helped the firm and its clients navigate through tough market cycles and catastrophic events, while constantly keeping a keen eye on opportunities for growth and expansion.”
O’Halleran said it has been an “absolute privilege to serve Aon over the last 37 years”.
He added: “At every turn, I have always been amazed at the resilience of our clients, markets and communities as we have navigated natural catastrophes, adapted to the rise of alternative capital and kept pace with the demands of our evolving industry. We have withstood these challenges and emerged stronger, while helping to raise awareness of new global exposures in the hope that future generations will be better prepared to deal with these emerging risks.”