Southampton, officially the Town of Southampton, is a municipality located in southeastern Suffolk County, New York, United States. It sits partly on the South Fork of Long Island, bounded by the Atlantic Ocean to the south and Peconic Bay to the north. The town shares borders with East Hampton to the east, Brookhaven to the west, and a small border with Riverhead to the northwest. As an incorporated town, it serves as a significant administrative unit within the region, encompassing seven incorporated villages and sixteen unincorporated areas known as hamlets.

The town was founded in 1640 when settlers from Lynn, Massachusetts, established residence on lands obtained from the local Shinnecock Indian Nation. The first group included eight men, one woman, and a boy who arrived at Conscience Point, with boundaries determined by July of that year. From 1644, colonists established an organized whale fishery, marking the first in New England. The town is named after the port city of Southampton in Hampshire, England, and its oldest existent house is the Halsey House, built by early settler Thomas Halsey.

Southampton is included in the stretch of shoreline prominently known as the Hamptons. The town contains notable sites such as the Shinnecock Hills Golf Club, which is claimed as an Indian burial ground, and operates an official historical website detailing over 100 points of interest. It has 47 public and private cemeteries and is home to Stony Brook University, which maintains a campus in the area. The town also features the Basilica of the Sacred Hearts of Jesus and Mary and numerous historic districts listed on the National Register.

The community draws visitors through its coastal geography and high-profile residential areas. In 2016, the zip code encompassing Sagaponack was listed as the most expensive in the U.S., with a median home sale price of $8.5 million. The area is known for its cultural figures, including fashion designer Calvin Klein, actor Michael J. Fox, and writer P. G. Wodehouse. Media presence includes the Southampton Press and various radio stations broadcasting across the region, contributing to its distinct social and economic character.

As of the 2020 U.S. census, the town had a population of 69,036. The economy is supported by major employers and tourism, with transportation provided by the Long Island Rail Road's Montauk Branch and Suffolk County Transit bus routes. The Francis S. Gabreski Airport and Southampton Heliport offer air access, while a ferry connects North Haven to Shelter Island. The town experiences a hot-summer humid continental climate bordering a humid subtropical zone, with one to two months averaging below freezing and six months above 50 °F.