Northumberland—Peterborough South (provincial electoral district)

Northumberland—Peterborough South is a provincial electoral district in Ontario, Canada, that has been represented in the Legislative Assembly of Ontario since the 2018 provincial election. It was created by the Representation Act, 2015, which merged the majority of the former riding of Northumberland—Quinte West with a portion of the former riding of Peterborough.

The riding primarily encompasses the southern portions of Northumberland County and the southeastern portion of Peterborough County. It includes the municipalities of Cobourg, Port Hope, and Trent Hills in Northumberland, as well as the townships of Cavan Monaghan and Otonabee-South Monaghan in Peterborough County. The southern boundary is Lake Ontario.

Prior to 2018, the area was largely represented by the Northumberland—Quinte West riding, which was known for its agricultural lands and communities along the Highway 401 corridor. The creation of Northumberland—Peterborough South reflects population shifts and redistribution across the province to ensure equitable representation. The riding is considered a bellwether, often electing a Member of Provincial Parliament (MPP) from the party that forms the government. Its economy is diverse, including agriculture, manufacturing, tourism, and a growing number of residents who commute to the Greater Toronto Area for work.