William Austin Mahoney (1871–1952) was a Canadian architect. During the first half of the 20th century, Mahoney was the leading architect in Guelph, Southwestern Ontario.[1] Mahoney brother, Harry, was mayor of Guelph in 1935–36.[2] Among the many buildings attributed to him, Mahoney designed several Carnegie libraries in Ontario: Aylmer, Campbellford, Elmira, Exeter, Fergus, Forest, Fort Frances, Kingsville, Midland, Parkhill, Port Hope, Stirling, Tillsonburg, Watford, and Whitby.[3]