The Magnetawan River is a long river in Parry Sound District, Ontario, Canada. The river flows 175 km from its source of Magnetawan Lake inside Algonquin Provincial Park to empty into Georgian Bay at the community of Britt on Byng Inlet. The name of the river means "swiftly flowing waters" in the Ojibwa language. At the end of the 19th century, the river was used to float white pine logs to sawmills downstream. The river gained recent renown when it was featured in Bill Mason's film Waterwalker.