Upper Darby Township, often shortened to Upper Darby, is a home rule township in Delaware County, Pennsylvania, United States. As of the 2020 census, the township had a total population of 85,681, making it the state's sixth-most populated municipality after Philadelphia, Pittsburgh, Allentown, Reading, and Erie. Upper Darby borders Philadelphia, the nation's sixth-most populous city, and constitutes part of the Delaware Valley, also known as the Philadelphia metropolitan area, the nation's seventh-largest metropolitan area.

Delaware County, colloquially referred to as Delco, is a county in the Commonwealth of Pennsylvania. With a population of 576,830 as of the 2020 census, it is the fifth-most populous county in Pennsylvania and the third-smallest in area. The county was created on September 26, 1789, from part of Chester County and named for the Delaware River. The county is part of the Southeast Pennsylvania region of the state.