Ballston–MU is a side platformed Washington Metro station in Arlington, Virginia, United States. The station opened on December 1, 1979, and is operated by the Washington Metropolitan Area Transit Authority (WMATA). The station serves the Orange and Silver Lines. The station serves the transit-oriented community of Ballston, Ballston Common Mall as well as Marymount University (MU). Ballston-MU is also a major Metrobus transfer station.