The Town of Southold is one of ten towns in Suffolk County, New York, United States. It is located in the northeastern tip of the county, on the North Fork of Long Island. The population was 23,732 at the 2020 census. The town also contains a hamlet named Southold, which was settled in 1640.

Suffolk County is the easternmost county in the U.S. state of New York. It is bordered to its west by Nassau County, to its east by Gardiners Bay and the Atlantic Ocean, to its north by Long Island Sound, and to its south by Great South Bay. The county is part of the Long Island region of the state, of which it comprises the eastern two-thirds.