Ridge is a hamlet and census-designated place (CDP) in the town of Brookhaven in Suffolk County, New York, United States. The population was 13,336 at the 2010 census.
Ridge is served by the Longwood Central School District, Ridge Fire Department, Suffolk County Police Department, Longwood Public Library, Suffolk County Water Authority, PSEG.
Ridge is located at 40°54′26″N 72°52′58″W (40.907128, -72.882909).
According to the United States Census Bureau, the CDP has a total area of 13.3 square miles (34.5 km2), of which 13.2 square miles (34.2 km2) is land and 0.077 square miles (0.2 km2), or 0.70%, is water.
Ridge is located at the northwestern end of the Long Island Pine Barrens Region and is referred to by a sign in the center of the hamlet as the "Gateway to the Pine Barrens".
In 1693, William "Tangier" Smith, who owned a homestead in Setauket, was allowed to purchase a large tract of land on the South Shore of Long Island in recognition of his being mayor of Tangier in Africa. The land, called St. George's Manor, stretched from the Carmans River (then called the Connecticut River) in the west to the edge of Town of Southampton in the east with a northern border around present-day New York State Route 25, as much as 81,000 acres (330 km2) of land. He made his manor seat on the South Shore in present-day Mastic, and the northern part, now the south side of Ridge, was called "The Swamp" or "Longswamp". A house wasn't built at Longswamp until after the American Revolution. In 1817, William Sydney Smith inhabited the house and changed the name to Longwood.
In 1955, what then remained of William Smith's original manor was primarily located in Ridge and was surrounded by the world growing up around it, in the form of the Brookhaven National Laboratory and the surrounding areas becoming increasingly populated. Longwood's 750 acres (300 ha) fell into the hands of Elbert Clayton Smith, who immediately moved his family from California to live there.