The Castor River is a river in eastern Ontario, in Canada. It flows into the South Nation River near Casselman. It has a number of branches, including the North, Middle, South and East Castor Rivers which join in Embrun. The river was named for the many beaver dams found in its watershed; "castor" means "beaver" in French.
Coordinates: 45°17′58″N 75°06′33″W / 45.29944°N 75.10917°W