The Ganaraska River is a river in Northumberland County and the Regional Municipality of Durham in Southern Ontario, Canada. It is part of the Great Lakes Basin, and is a tributary of Lake Ontario, which it reaches at the central community of the municipality of Port Hope. The river's name is thought to originate from Ganaraske, the name for the Cayuga village which was located at the current site of Port Hope.CourseThe river begins on the Oak Ridges Moraine in the Ganaraska Forest in the municipality of Clarington, about 1.5km southeast of the junction of Ontario Highway 35 and Ontario Highway 115. It flows southeast past the community of Kendal, takes in the left tributary North Ganaraska RIver, then turns south to its mouth on the north shore of Lake Ontario.WatershedPortions of the Ganaraska River drainage basin of 278km2 extend into the City of Kawartha Lakes; the Township of Cavan–Monaghan, Peterborough County; and the Township of Hamilton, Northumberland County.