Fort Lafayette was an island coastal fortification in the Narrows of New York Harbor, built offshore from Fort Hamilton at the southern tip of what is now Bay Ridge in the New York City borough of Brooklyn. The fort was built on a natural island known as Hendrick's Reef. Construction on the fort began during the War of 1812 and was completed in 1822. The fort, originally named Fort Diamond after its shape, was renamed in 1823 to celebrate the Marquis de La Fayette, a hero of the American Revolution who would soon commence a grand tour of the United States. During the American Civil War, the island fort became a prison, mostly for civilians viewed as disloyal to the Union; the fort became known as an "American Bastille." The fort was demolished in 1960 to make room for the Verrazzano-Narrows Bridge; the Brooklyn-side bridge tower now occupies the fort's former foundation site.

The Narrows is the tidal strait separating the boroughs of Staten Island and Brooklyn in New York City. It connects the Upper New York Bay and Lower New York Bay and forms the principal channel by which the Hudson River empties into the Atlantic Ocean. It has long been considered to be the maritime "gateway" to New York City and historically has been one of the most important entrances into the harbors of the Port of New York and New Jersey.