The Nissequogue River is an 8.3-mile (13.4 km) long river flowing from Smithtown, New York into the Long Island Sound. Its average discharge of 42.2 cubic feet per second (1.19 m3/s) is the most of any of the freshwater rivers on Long Island. The river, like all other freshwater rivers on the island, is totally derived from groundwater (not from lakes). Its name is derived from one of the Algonquian-speaking Nissequaq tribe in the area.