Fort Greene is a neighborhood in the northwestern part of the New York City borough of Brooklyn. The neighborhood is bounded by Flushing Avenue and the Brooklyn Navy Yard to the north, Flatbush Avenue Extension and Downtown Brooklyn to the west, Atlantic Avenue and Prospect Heights to the south, and Vanderbilt Avenue and Clinton Hill to the east. The Fort Greene Historic District is listed on the New York State Registry and on the National Register of Historic Places, and is a New York City designated historic district.

The neighborhood is named after an American Revolutionary War era fort that was built in 1776 under the supervision of General Nathanael Greene of Rhode Island. General Greene aided General George Washington during the Battle of Long Island in 1776. Fort Greene Park, originally called "Washington Park" is Brooklyn's first. In 1864, Fort Greene Park was redesigned by Frederick Law Olmsted and Calvert Vaux; the park notably includes the Prison Ship Martyrs' Monument and crypt, which honors some 11,500 patriots who died aboard British prison ships during the American Revolution.

Fort Greene contains many examples of mid-19th century Italianate and Eastlake architecture, most of which is well preserved. It is known for its many tree-lined streets and elegant low-rise housing. Fort Greene is also home to the Williamsburgh Savings Bank Tower, which, for over 80 years, was the tallest building in Brooklyn. The neighborhood is close to the Atlantic Terminal station of the Long Island Rail Road and has access to many New York City Subway services.

Fort Greene is part of Brooklyn Community District 2, and its primary ZIP Codes are 11201, 11205, 11217, and 11238. It is patrolled by the 88th Precinct of the New York City Police Department. Politically it is represented by the New York City Council's 35th District. Fort Greene, a largely African-American neighborhood in the 20th century, has been significantly gentrified over the years, with the Black population decreasing from 41.8% in 2000 to 25.8% in 2017.

In approximately A.D. 800, a gradual movement of Native Americans advanced from the Delaware area into lower New York, ultimately settling as part of the Canarsie tribe among 13 tribes of the Algonquin Nation. In 1637, Walloon reformed Joris Jansen Rapelje purchased 335 acres (1.36 km²) of Native American land from Dutch West India Company in the area of Brooklyn that became known as Wallabout Bay (from Waal Boght or "Bay of Walloons"). This is the area where the Brooklyn Navy Yard now stands on the northern border of Fort Greene. An Italian immigrant named Peter Caesar Alberti started a tobacco plantation near the bay in Fort Greene in 1649 but was killed six years later by Native Americans. In 1776, under the supervision of General Nathanael Greene of Rhode Island the American Revolutionary War era Fort Putnam was constructed. Later renamed after Greene, the fort was a star-shaped earthwork that mounted six 18-pound cannons, and was the largest on Long Island. After the American defeat in the Battle of Long Island, George Washington withdrew his troops from the Fort under the cover of darkness, a brilliant move that saved the outnumbered American army from total defeat by the British. Although the fort was repaired in advance of an expected attack on Brooklyn by the British during the War of 1812, it thereafter slowly deteriorated.

In 1801, the U.S. government purchased land on Wallabout Bay for the construction of the Brooklyn Navy Yard, stimulating some growth in the area. Ferry service linking Manhattan and Brooklyn launched in 1814, and Brooklyn's population exploded from 4,000 to nearly 100,000 by 1850.^{[citation needed]} Fort Greene was known as The Hill and was home to a small commuter population, several large farms—the Post Farm, the Spader farm, the Ryerson Farm, and the Jackson farm—and a burial ground. As early as the 1840s the farms' owners began selling off their land in smaller plots for development. Country villas, frame row houses, and the occasional brick row house dotted the countryside, and one of them was home to poet Walt Whitman, editor of the Brooklyn Eagle newspaper.

Since the early 19th century, African Americans have made significant contributions to Fort Greene's development. New York State outlawed slavery in 1827 and 20 years later "Coloured School No. 1," Brooklyn's first school for African-Americans, opened at the current site of the Walt Whitman Houses. Abolitionists formed the Lafayette Avenue Presbyterian Church in 1857, and hosted speakers such as Frederick Douglass and Harriet Tubman and also aided in the work of the Underground Railroad. Skilled African-American workers fought for their rights at the Navy Yard during the tumultuous Draft Riots of 1863 against armed hooligan bands. The principal of P.S. 67 in the same year was African American, and Dr. Phillip A. White became the first black member of Brooklyn's Board of Education in 1882. By 1870, more than half of the Black population in Brooklyn lived in Fort Greene, most of them north of Fort Greene Park.

In the 1850s, Fort Greene's growth spread out from stagecoach lines on Myrtle Avenue and Fulton Street that ran to Fulton Ferry, and The Hill became known as the home of prosperous professionals, second only to Brooklyn Heights in prestige. During the 1850s and 1860s, blocks of Italianate brick and brownstone row houses were built on the remaining open land to house the expanding upper and middle class population. The names of the most attractive streets (Portland, Oxford, Cumberland, Carlton, and Adelphi) came from fine Westminster terraces and streets of the early 19th century. By the 1870s, construction in the area had virtually ended, and the area still maintains hundreds of Italianate, Second Empire, Greek Revival, Neo-Grec, Romanesque Revival and Renaissance Revival row houses of virtually original appearance.