The Brooklyn Navy Yard (originally known as the New York Navy Yard) is a shipyard and industrial complex in northwest Brooklyn in New York City, New York, U.S. The Navy Yard is located on the East River in Wallabout Bay, a semicircular bend of the river across from Corlears Hook in Manhattan. It is bounded by Navy Street to the west, Flushing Avenue to the south, Kent Avenue to the east, and the East River on the north. The site, which covers 225.15 acres (91.11 ha), is listed on the National Register of Historic Places.

The Brooklyn Navy Yard was established in 1801. From the early 1810s through the 1960s, it was an active shipyard for the United States Navy, and was also known as the United States Naval Shipyard, Brooklyn and New York Naval Shipyard at various points in its history. The Brooklyn Navy Yard produced wooden ships for the U.S. Navy through the 1870s. The shipyard built the USS Monitor, the Navy's first ironclad warship, in 1862, and it transitioned to producing iron vessels after the American Civil War in the mid-1860s. It produced some of the Navy's last pre-dreadnought battleships just prior to World War I, and it performed major repairs and overhauls of its dreadnought and post-dreadnought battleships during World War II.

The Brooklyn Navy Yard has been expanded several times, and at its peak, it covered over 356 acres (144 ha). The efforts of its 75,000 workers during World War II earned the yard the nickname "The Can-Do Shipyard". The Navy Yard was deactivated as a military installation in 1966, but continued to be used by private industries. The facility now houses an industrial and commercial complex run by the New York City government, both related to shipping repairs and maintenance and as office and manufacturing space for non-maritime industries.

The Brooklyn Navy Yard includes dozens of structures, some of which date to the 19th century. The Brooklyn Naval Hospital, a medical complex on the east side of the Brooklyn Navy Yard site, served as the yard's hospital from 1838 until 1948. Dry Dock 1, one of six dry docks at the yard, was completed in 1851 and is listed as a New York City designated landmark. Former structures include Admiral's Row, a grouping of officers' residences at the west end of the yard, which was torn down in 2016 to accommodate new construction. Several new buildings were built in the late 20th and early 21st centuries as part of the city-run commercial and industrial complex. A commandant's residence, also a National Historic Landmark, is located away from the main navy yard site. The FDNY's Marine Operations Division and their fireboats are located at Building 292.

The site of the Brooklyn Navy Yard was originally a mudflat and tidal marsh settled by the Canarsie Indians. The Dutch colonized the area in the early 17th century, and by 1637, Dutch settler Joris Jansen Rapelje purchased 335 acres (136 ha) of land around present-day Wallabout Bay from the Indians. The site later became his farm, though Rapelje himself did not reside on it until circa 1655. Rapelje was a Walloon from Belgium, and the area around his farm came to be known as "Waal-boght" or "Waal-bocht", which translates roughly into "Walloon's Bay"; this is probably where the name of Wallabout Bay was adapted from. The Rapelje family and their descendants had possession of the farm for at least a century afterward, and mostly farmed on the drained mudflats and tidal marshland. They built a grist mill and a mill pond on the site by 1710. The pond continued to be used through the 19th century. The Remsen family were the last descendants of the Rapeljes to own the farm, and they held possession of nearby land plots through the mid-19th century.

During the American Revolutionary War, the British held American prisoners of war on prison ships moored in the bay. Many of the prisoners died and were buried in trenches on nearby ground. Some 12,000 prisoners were said to have died by 1783, when the remaining prisoners were freed. The Prison Ship Martyrs' Monument in nearby Fort Greene was built to honor these casualties. In 1781, shipbuilder John Jackson and two of his brothers acquired different parts of the Rapelje estate. Jackson went on to create the neighborhood of Wallabout, as well as a shipbuilding facility on the site. The first ship that Jackson built at the site was the merchant ship Canton, which he built in the late 1790s.

The Jacksons put the land up for sale in 1800, and the federal government soon learned about the sale. On February 7, 1801, federal authorities purchased the old docks and 40 acres (16 ha) of land from John Jackson for $40,000 through an intermediary, Francis Childs. Childs sold the site to the federal government 16 days later. The purchase was part of outgoing U.S. president John Adams's plans to establish a series of naval yards in the United States. This particular site was chosen because it was thought that the plot's location near Lower Manhattan and New York Harbor would be ideal for placing military defenses; however, this never came to fruition.

The property went unused for several years because Adams's successor Thomas Jefferson opposed military build-up. The Brooklyn Navy Yard became an active shipyard for the United States Navy in 1806, when the yard's first commandant Jonathan Thorn moved onto the premises. It took several decades before the Brooklyn Navy Yard was fully developed; for the most part, early development was focused around the western side of the current yard. It was around the same time that Quarters A, the federal-style commandant's house, was built at the northwestern corner of the Brooklyn Navy Yard. In 1810, the federal government acquired another 131 acres (53 ha) of land from the state of New York. Much of this land was underwater at high tide. During the War of 1812, the Brooklyn Navy Yard repaired and retrofitted more than 100 ships, although it was not yet used for shipbuilding.