|Origin||Lakeland County Park,
Islandia, New York
|Mouth||Nicholls Bay on the Great South Bay|
|Basin countries||United States|
|Length||6 mi (10 km)|
|Source elevation||50 feet (15 m)|
|Basin area||4,500 acres (7 sq mi)|
The Connetquot River (also known as Great River) is a 6 mi (10 km) long river in Islip. It is one of the four biggest rivers on Long Island and is recognized by the state as a Wild, Scenic and Recreational River.
It starts just south of the Long Island Expressway from springs in the Lakeland County Park in Islandia, New York where it is called Connetquot Brook. The estuary portion south of Sunrise Highway at Oakdale, New York is officially called the Connetquot River although in popular usage both the brook and river share the same name.
The Connetquot River habitat is the largest contiguous area of undeveloped land in Suffolk County that encompasses an entire river watershed. It, like all other rivers on Long Island, is totally generated from groundwater springs (no lakes).