The Nottawasaga River is a river in Simcoe County and Dufferin County in Central Ontario, Canada. It is part of the Great Lakes Basin, and is a tributary of Lake Huron. The river flows from the Orangeville Reservoir in the town of Orangeville, Dufferin County, through the Niagara Escarpment and the Minesing Wetlands, the latter a wetland of international significance (Ramsar Convention site), and empties into Nottawasaga Bay, an inlet of Georgian Bay on Lake Huron, at the town of Wasaga Beach, Simcoe County.