Blockhouse No. 1, colloquially known as The Blockhouse, is a small fort in the North Woods section of Central Park, Manhattan, New York City. Finished in 1814, the Blockhouse is the second-oldest structure in the park, after Cleopatra's Needle, and the oldest surviving structure originally built within the park site. It is located on an overlook of Manhattan schist, with a clear view of the flat surrounding areas north of Central Park.

A blockhouse is a small fortification, usually consisting of one or more rooms with loopholes, allowing its defenders to fire in various directions. It is usually an isolated fort in the form of a single building, serving as a defensive strong point against any enemy that does not possess siege equipment or, in modern times, artillery, air force or cruise missiles. A fortification intended to resist these weapons is more likely to qualify as a fortress or a redoubt, or in modern times, be an underground bunker. However, a blockhouse may also refer to a room within a larger fortification, usually a battery or redoubt.