William Trench III (October 21, 1831 - April 12, 1896) was the reeve of Richmond Hill, Ontario from 1875–1879 and 1881 - 1882. Born in Dunbar, Scotland, Trench came to Elgin Mills, Ontario with his family in 1842. Trench learned the blacksmith trade from his father and set up a shop in Richmond Hill in 1857. In 1866, Richmond Hill set up its first fire brigade, and Trench was chosen the first fire chief.