Peterborough is a city on the Otonabee River in Ontario, Canada, about 125 kilometres northeast of Toronto. According to the 2021 Census, the population of the City of Peterborough was 83,651. The population of the Peterborough Census Metropolitan Area, which includes the surrounding Townships of Selwyn, Cavan Monaghan, Otonabee-South Monaghan, and Douro-Dummer, was 128,624 in 2021.