Fort Wadsworth is a former military installation on Staten Island, New York. Situated on the Narrows, which divides New York Bay into Upper and Lower halves, it was closed in 1994; prior to that it had been the longest continually-manned military installation in the United States.

The first use of the land for military purposes was as the site of a blockhouse in 1663. During the American Revolution it became known as Flagstaff Fort; captured by the British in 1776, it remained in British hands until the war's end in 1783. It became the responsibility of New York State in 1806, and reverted to federal control during the War of 1812. Divided into several smaller units, including Fort Tompkins and Fort Richmond, its present name was adopted in 1864 to honor Brigadier General James Wadsworth, who had been killed in the Battle of the Wilderness during the Civil War.

By 1924, Fort Wadsworth had become an infantry post, and from 1955 until 1974 it was the headquarters of the 52nd AAA Brigade. It then was the site of the United States Army Chaplain school before being turned over to the United States Navy in 1979, which used it as the headquarters of its New York Naval Station. The property became part of the Gateway National Recreational Area when the Navy left in 1994.

The name "Fort Wadsworth" is also sometimes used to denote the residential neighborhood surrounding the former fort, south of Rosebank and north of South Beach. This neighborhood once had a station on the South Beach Branch of the Staten Island Railway; service on this branch ceased in 1953.