The Santuit River, also known as the Cotuit River, is a 2.3-mile-long river on the border between Mashpee and Cotuit on Cape Cod.

The river flows southwards from the southern end of Santuit Pond into Popponesset Bay (also known as Shoestring Bay) on the south shore of Cape Cod.

The river was a vigorous herring/alewife run and has been reputed to hold sea-run brown trout.