The German reunification was the process in 1990 in which the German Democratic Republic (GDR/East Germany) joined the Federal Republic of Germany (FRG/West Germany) to form the reunited nation of Germany, and when Berlin reunited into a single city, as provided by its then Grundgesetz constitution Article 23. The end of the unification process is officially referred to as German unity , celebrated on 3 October (German Unity Day) .