Upper Darby Township (often shortened to simply Upper Darby) is a home rule township in Delaware County, Pennsylvania, United States, bordering the city of Philadelphia on land formerly inhabited by the Lenape Tribal Nation. Upper Darby is home to the Tower Theater, a historic music venue on 69th Street built in the 1920s. Upper Darby's population is diverse, representing over 100 ethnic cultures. The township hosts a range of housing types including densely populated rowhouse sections similar to houses in neighboring West Philadelphia, tree-lined neighborhoods of turn-of-the-century single-family houses and mid-century developments. It is Pennsylvania's sixth most populous municipality.
Upper Darby is 65% residential, 25% commercial, and 8% other. As of the 2010 census, the township had a total population of 82,795. Because of a home-rule charter adopted in 1974 and effective in 1976, Upper Darby utilizes a mayor-council form of management, unlike communities that are still under the Pennsylvania Township Code. ("First Class" townships in Pennsylvania have a board of commissioners and are divided into wards, and "Second Class" townships have a board of supervisors, which are usually elected "at-large".)
Upper Darby, along with Lower Merion, Haverford, and Cheltenham form the major inner ring western suburbs of Philadelphia.
In 1650, the area that eventually became Upper Darby had been inhabited by the Lenape tribe of Native Americans for hundreds of years, but war with the Susquehannock to the west, along with devastating smallpox and measles epidemics, had significantly reduced their numbers.