Dead Horse Bay is a small water body off Barren Island between the Gerritsen Inlet and Rockaway Inlet in the New York City borough of Brooklyn.

From the nineteenth century to the twentieth century the area has been used in a variety of ways, including manufacturing fertilizer from the remains of dead animals and more recently a landfill for the disposal of New York City’s garbage. A millstone used to ground horse bones can still be found along the Millstone trail. In 1926, much of the salt marsh surrounding Dead Horse Bay and the rest of Barren Island were pumped with sand from Jamaica Bay. This raised the land to 16 feet above the high tide mark and connected the islands to each other, and the mainland of Brooklyn, in order to create Floyd Bennett Field as New York City's first municipal airport. The entire area, including the historic airfield, are now managed by the National Park Service as part of the Jamaica Bay Unit of the Gateway National Recreation Area.