is a hamlet (and a census-designated place) in Suffolk County, New York, United States. The population was 3,646 at the 2000 census. It is the location of the Big Duck.
It is located on the south side of the Peconic River at its mouth in Peconic Bay. Riverhead is across the river to the north.
According to the United States Census Bureau, the CDP has a total area of 14.8 square miles (38.3 km²), of which, 12.3 square miles (31.8 km²) of it is land and 2.5 square miles (6.5 km²) of it (17.04%) is water.