William James Topley (13 February 1845 – 16 November 1930) was a Canadian photographer based in Ottawa, Ontario. He was the best known of Ottawa’s nineteenth-century photographers and the most socially prominent one. Topley was noted for his portraiture of Canadian politicians and was a business partner of William Notman, having taken over Notman's Ottawa studio in 1872. A large number of photographs by Topley are now in the collection of Library and Archives Canada, including approximately 150,000 glass plates negatives and a set of 66 index albums covering the entire history of his Ottawa studios from 1868 until 1923.