West Chester is a borough and the county seat of Chester County, Pennsylvania, United States. Located within the Philadelphia metropolitan area, the borough had a population of 18,461 at the 2010 census. West Chester is the mailing address for most of its neighboring townships. When calculated by mailing address, the population as of the 2010 U.S. Census was 108,696, which would make it the 10th largest city by mailing address in the state of Pennsylvania.

Chester County, colloquially referred to as Chesco, is a county in the Commonwealth of Pennsylvania. It is located in the Delaware Valley region, located in the southeastern part of the state. As of the 2020 census, the population was 545,823(As of 2022), increasing by 7.1% from 498,886 in 2010. The county seat is the Borough of West Chester. The most populous of its 73 municipalities is Tredyffrin Township. The most populous boroughs are West Chester and Phoenixville. Coatesville is the only municipality in the County organized under the City form of government, a technical rather than demographic distinction. Chester County was one of the three original Pennsylvania counties created by William Penn in 1682. It was named for Chester, England. The county is part of the Southeast Pennsylvania region of the state.