Peterborough West was a federal electoral district represented in the House of Commons of Canada from 1867 to 1953. It was located in the province of Ontario. It was created by the British North America Act of 1867 which divided the County of Peterborough was into two ridings. The West Riding consisted of the Townships of South Monaghan (in the County of Northumberland), North Monaghan, Smith, and Ennismore, and the Town of Peterborough.
In 1903, the townships of Cavendish, Galway, Harvey, and the village of Ashburnham were added to the riding. In 1914, the village of Ashburnham was excluded.
In 1924, Peterborough West was defined to consist of the part of the county of Peterborough included in the townships of Galway, Cavendish, Harvey, Ennismore, Smith, Douro, Otanabee and North Monaghan, and that part of the county of Northumberland included in the township of South Monaghan, together with the city of Peterborough. In 1947, South Monaghan was excluded from the riding.
The electoral district was abolished in 1952 when it was merged into Peterborough riding.
This riding elected the following members of the House of Commons of Canada: