Pennsylvania's fifth congressional district encompasses all of Delaware County, an exclave of Chester County, a small portion of southern Montgomery County and a section of southern Philadelphia. Democrat Mary Gay Scanlon represents the district.

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.