Mill Basin is a residential neighborhood in southeastern Brooklyn, New York City. It is on a peninsula abutting Jamaica Bay and is bordered by Avenue U on the northwest and the Mill Basin/Mill Island Inlet on its remaining sides. Mill Basin is adjacent to the neighborhood of Bergen Beach to the northeast, Flatlands to the northwest, Marine Park to the southwest, and Floyd Bennett Field and the former Barren Island to the southeast. Mill Basin also contains a subsection called Old Mill Basin, north of Avenue U.

Mill Basin was originally Mill Island, Jamaica Bay. In the 17th century, a mill was built on Mill, Bergen, and Barren Islands. The archipelago was then occupied by the Schenck and Crooke families through the late 19th century, and remained a mostly rural area with oyster fishing. After Robert Crooke developed a smelting plant on Mill Island in 1890, industrial customers started developing the island and connected it to the rest of Brooklyn. In an effort to develop Mill Basin as a seaport district, ports and dry docks were built in the early 20th century, though a lack of railroad connections hindered the area's further growth. Residential development began in the 1950s, along with the rest of southeast Brooklyn, though some of the former industrial buildings remain.

Mill Basin has some of the most luxurious houses in New York City, though it also contains commercial and industrial tenants, as well as the Kings Plaza shopping mall in its western part. The area around Mill Basin consists of a mostly white population as of the 2010 United States Census, and is sparsely served by public transportation. Nearby recreational areas include Floyd Bennett Field, the first municipal airport in New York City, which is part of the Gateway National Recreation Area and is just southeast of Mill Basin.