Catharpin is an unincorporated community in Prince William County, Virginia, in the United States. Catharpin lies on State Route 234 to the northwest of Manassas National Battlefield Park.Catharpin is characterized by rolling fields, wide meadows, and gravel/dirt roads, and many of the rural folk capitalize on the abundant land and have farms with livestock. It is not uncommon to see horses roaming on 50 acres of land.