1. Fußballclub Union Berlin e. V., commonly known as 1. FC Union Berlin (German pronunciation: [ˈeːɐ̯stɐ ʔɛfˈtseː ʔuˈni̯oːn bɛʁˈliːn]) or simply Union Berlin, is a professional German association football club based in the locality of Köpenick of the borough of Treptow-Köpenick of Berlin.