Peterborough West was a federal electoral district represented in the Canadian House of Commons 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.