Fußballclub Union Berlin - more commonly known as FC Union Berlin or simply Union Berlin - is a German football club based in Köpenick close to Berlin, Germany. They play their home games at the Stadion An der Alten Försterei.
Though officially founded in 1966, the club has origins as far back as 1906 when its predecessor FC Olympia Oberschöneweide was inaugurated. Based in East Berlin during the Cold War, they joined the German league structure after the reunification in 1990. From 2009 to 2019, they played in the 2. Bundesliga, German football's second division and, in 2019, they were promoted to the Bundesliga. The club has a community ethos and the fans even rebuilt the stadium in 2008 when it needed redevelopment. The club is known as Die Eisernen meaning the "Iron Ones" and the fans have a chant called "Eisern Union" ("Iron Union").