William Erskine Knowles (November 28, 1872 – July 17, 1951) was a Canadian politician.

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.

Knowles resigned his seat in the Saskatchewan assembly in 1927 after he was named a judge.

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