Pennsylvania's 10th congressional district is located in the south-central region of the state. It encompasses all of Dauphin County as well as parts of Cumberland County and York County. The district includes the cities of Harrisburg and York. Prior to 2019, the district was located in the northeastern part of the state. The Supreme Court of Pennsylvania redrew the district in 2018 after ruling the previous map unconstitutional because of gerrymandering. The court added State College to the old district's boundaries while removing some Democratic-leaning areas and redesignated it the twelfth district; an area encompassing Harrisburg and York was numbered as the "10th". The new tenth district is represented by Republican Scott Perry, who previously represented the old fourth district.

Dauphin County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 286,401. The county seat is Harrisburg, Pennsylvania's state capital and ninth-most populous city. The county was created on March 4, 1785, from part of Lancaster County and was named after Louis Joseph, Dauphin of France, the first son of King Louis XVI. The county is part of the South Central Pennsylvania region of the state.