Cobourg is a town in the Canadian province of Ontario, located in Southern Ontario 95 km (59 mi) east of Toronto and 62 km (39 mi) east of Oshawa. It is the largest town in and seat of Northumberland County. Its nearest neighbour is Port Hope, 7 km (4 mi) to the west. It is located along Highway 401 and the former Highway 2. To the south, Cobourg borders Lake Ontario. To the north, east and west, it is surrounded by Hamilton Township.

Northumberland County is an upper-tier municipality situated on the north shore of Lake Ontario, east of Toronto in Central Ontario. The Northumberland County headquarters are located in Cobourg.