The Town of Brookhaven is one of the ten towns into which Suffolk County, New York, United States has been divided. Part of the New York metropolitan area, it is located in central Suffolk County and is the only town in the county that stretches from the North Shore to the South Shore of Long Island. The population of the town was 448,248 at the 2000 census. It is the largest town (by area, if including water area) in the state of New York, and the second most populous, exceeded only by the Town of Hempstead in Nassau County.
According to the United States Census Bureau, the town has a total area of 531.5 square miles (1,376.6 km²), of which 259.3 square miles (671.6 km²) is land and 272.2 square miles (705.1 km² or 51.22%) is water. It is the largest town in New York in terms of total area. Excluding water, however, there are four towns in the state with more land area: Webb in Herkimer County, Long Lake in Hamilton County, Arietta in Hamilton County, and Ohio in Herkimer County.
It has coastline on both the Atlantic Ocean and Long Island Sound. Riverhead and Southampton lie to the east, and Smithtown and Islip lie to the west.