The River Cam is a tributary of the River Great Ouse in the east of England. The two rivers join to the south of Ely at Pope's Corner.^{map 1} The Great Ouse connects the Cam to England's canal system (via the Middle Level Navigations and the River Nene) and to the North Sea at King's Lynn. The total distance from Cambridge to the sea is about 40 mi (64 km).

In earlier times the Cam was named the Granta, but after the name of the Anglo-Saxon town of Grantebrycge had been modified to Cambridge, the river was renamed to match. It has no connection with the much smaller River Cam in Gloucestershire.

It has been said that the River is the "Granta" above the Silver Street Bridge^{map 11} (in Cambridge) and the "Cam" below it.