The Severn River is a river in central Ontario, Canada. Its headwaters are located at the north end of Lake Couchiching. It drains Lake Couchiching and Lake Simcoe. The river flows generally northwest into Georgian Bay, a large bay of Lake Huron. The Severn forms part of the inland canal system known as the Trent–Severn Waterway, which links Port Severn on Georgian Bay with Trenton on Lake Ontario via the Trent Canal.