William Erskine Knowles (November 28, 1872 – July 17, 1951) was a Canadian politician. Born in Alliston, Ontario, Knowles was educated at Osgoode Hall Law School in Toronto, Ontario. A lawyer by profession, he was first elected to the House of Commons of Canada for the electoral district of Assiniboia West in a by-election held on February 6, 1906. A Liberal, he was re-elected in 1908 and 1911 for the electoral district of Moose Jaw. He did not run in 1917. From 1918 to 1927, he was a member of the Legislative Assembly of Saskatchewan. From 1918 to 1921, he was the Provincial Secretary and from 1919 to 1921 he was the Minister of Telephones. He attempted a federal comeback in the 1921 and 1923 elections but was defeated. Knowles resigned his seat in the Saskatchewan assembly in 1927 after he was named a judge.

Electoral results (partial)

By-election: On Mr. Scott's resignation to enter provincial politics in Saskatchewan, 29 August 1905.