Don Callahan formally retired in 2025 after leading Guy Carpenter Canada, a subsidiary of Marsh McLennan Companies, as President and CEO. During part of his tenure in Canada, Don also managed Guy Carpenter Latin America including the Caribbean, Mexico and South America. Previously, he served in underwriting management roles at predecessor companies of Swiss Re and Odyssey Re. Don is a graduate of Lower Canada College and McGill University (as a University Scholar) in Montreal. He is an FCIP (top graduating fellow) and attended on-site and industry-specific executive programs at both Harvard and Stanford Universities.