The Muskoka River is a river in the Muskoka District of Ontario, Canada. The river is the third largest river draining the southern Ontario land mass by average annual flow. It rises in the highlands of Algonquin Park and flows southwest through a number of lakes including which empty into Georgian Bay south of Parry Sound by way of the Moon and Musquash Rivers. Tributaries include the: Communities on the river include: The name "Muskoka" comes from the name of a chief of the Ojibwa in this region, "Mesqua Ukee" (Miskwaa-aki: Red Earth).

In fiction

There is also a Muskoka River in Nancy Drew's fictional home town of River Heights, located somewhere in the Midwestern United States.