Halesite is a hamlet and census-designated place (CDP) in the Town of Huntington in Suffolk County, on the North Shore of Long Island, in New York, United States. The population was 2,498 at the 2010 census.

The North Shore of Long Island is the area along the northern coast of New York's Long Island bordering Long Island Sound. Known for its extreme wealth and lavish estates, the North Shore exploded into affluence at the turn of the 20th century, earning it the nickname the Gold Coast. Historically, this term refers to the affluent coastline neighborhoods of the towns of North Hempstead and Oyster Bay in Nassau County and Huntington in Suffolk County. Some definitions may also include the parts of Smithtown that face the Sound. The region is also largely coextensive with the Gold Coast region of Long Island, though this region excludes Smithtown, as the easternmost Gold Coast mansion is the Geissler Estate, located just west of Indian Hills Country Club in the Fort Salonga section of Huntington.