Southwest is the southwestern quadrant of Washington, D.C., the capital of the United States, and is located south of the National Mall and west of South Capitol Street. It is the smallest quadrant of the city, and contains a small number of named neighborhoods and districts, including Bellevue, Southwest Federal Center, the Southwest Waterfront, Buzzard Point, and the military installation known as Joint Base Anacostia–Bolling.

Washington, D.C., is administratively divided into four geographical quadrants of unequal size, each delineated by their ordinal directions from the medallion located in the Crypt under the Rotunda of the Capitol. Street and number addressing, centered on the Capitol, radiates out into each of the quadrants, producing a number of intersections of identically named cross-streets in each quadrant. Originally, the District of Columbia was a near-perfect square but contained more than one settlement; the Capitol was to be the center of the City of Washington. Thus, the Capitol was never located at the geographic center of the whole territory, which was eventually north of the Potomac River, consolidated into one city. As a result, the quadrants are of greatly varying size. Northwest is quite large, encompassing over a third of the city's geographical area, while Southwest is little more than a few neighborhoods, large parks, and a military base.