Morrisania (/ˌmɒrɪˈseɪniə/ MORR-ih-SAY-nee-ə) is a residential neighborhood in the southwestern Bronx, New York City, New York. Its boundaries are the Cross Bronx Expressway to the north, Crotona-Prospect Avenue to the east, East 163rd Street to the south, and Webster Avenue to the west. Third Avenue is the primary thoroughfare through Morrisania.

The name derives from the Manor of Morrisania, the 2,000-acre (810 ha) estate of the powerful and aristocratic Morris family, who at one time owned most of the Bronx as well as much of New Jersey. The family includes Lewis Morris, 4th Lord of the Manor and signatory to the United States Declaration of Independence, and Gouverneur Morris, the penman of the United States Constitution. Both are buried in the crypt at St. Ann's Church of Morrisania. Today the name is most commonly associated with the neighborhood of Morrisania, which is only a small corner of the original Morrisania.

Morrisania is part of Bronx Community Board 3, and its ZIP Codes include 10456 and 10459. The area is patrolled by the NYPD's 42nd Precinct. NYCHA property in the area is patrolled by P.S.A. 7 at 737 Melrose Avenue in the Melrose section of the Bronx.

From 1655 to the early 20th century, the land of the neighborhood was the estate of the Morris family in Westchester County. In 1790, Lewis Morris, owner of the estate and signer of the Declaration of Independence, proposed the land as the site of the federal capital.

The area was sparsely populated until 1840, when Gouverneur Morris Jr., son of the famous congressional delegate and nephew of Lewis, allowed a railroad to be built across the property. In 1848, he sold the land next to the line for the development of a new settlement called the Village of Morrisania. In 1855, additional settlements along the rail line became the Town of Morrisania (with its own police force), with its political center in the original 1840 village (which was eventually incorporated in 1864). At first, the village was an early forerunner of today's bedroom communities, populated by people who worked in Manhattan, but it quickly developed its own local industries and craftsmen as it developed into a full-fledged town. In 1874, the area was annexed to New York City (then consisting only of Manhattan) as part of the Twenty-Third Ward. In 1887, the Third Avenue Elevated was extended to the area to provide easy and quick access to and from Manhattan. By the time the New York City Subway was extended to the area in 1904, a large influx of Slavic immigrants had given the neighborhood an urban character, with a high concentration of tenement buildings replacing houses as the dominant form of dwelling.

In the 1950s along with changing demographics, Robert Moses destroyed various tenements in favor of a colony of public housing. After the construction of the Cross-Bronx Expressway, the poverty that East Tremont suffered spread into Morrisania. As a result, and also due to the aggressive 1968 Program for Action, the Third Avenue El closed in 1970. During this period, a wave of arson committed by a gang known as the Upper Streeters destroyed or damaged many of the residential, commercial, and industrial structures in the area.

Many social problems associated with poverty, from crime to drug addiction, have plagued the area for some time. Despite crime declines versus their peaks during the crack and heroin epidemics, violent crime continues to be a serious problem in the community. Morrisania has significantly higher drop-out rates and incidents of violence in its schools. Many households in the area are headed by single mothers, which contributes to the high poverty rate. Single-parent homes often have a harder time providing at the same level as two-parent homes. Many of the families living in Morrisania have been in poverty for generations. The incarceration rate in the area is also very high. Morrisania is home to a significant number of inmates currently held in New York state prison and jail facilities.

After a wave of arson ravaged the low-income communities of New York City throughout the 1970s, most of the residential structures in Morrisania were left seriously damaged or destroyed. The city began to rehabilitate many formally abandoned tenement-style apartment buildings and designate them as low-income housing beginning in the late 1970s. Also many subsidized attached multi-unit townhouses and newly constructed apartment buildings have been or are being built on vacant lots across the neighborhood.^{[citation needed]}