The Ganaraska River is a river that bisects the (original) Town of Port Hope, Ontario, Canada. From its headwaters in the Oak Ridges Moraine, it flows into the north shore of Lake Ontario. It is located in the western end of Northumberland County, Ontario.
It attracts anglers for salmon and trout. The Ganaraska River Fishway, a fish ladder, allows rainbow trout to travel up river to spawn.
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.