Mastic is a hamlet in Suffolk County, New York, United States. The population was 15,436 at the 2000 census. Mastic is a community located in the southeast part of the Town of Brookhaven. The hamlet was originally called Forge. The Long Island Rail Road built a station in 1882. In 1893, the name of the town was changed to Mastic. On July 15, 1960, the stop was moved 7010 feet west and renamed Mastic–Shirley. Mastic is served by the William Floyd School District and the Eastport-South Manor Central School District. The Poospatuck Indian Reservation lies entirely within the community, near its southern end.