On what date did German reunification formally take place?

German reunification formally took place on 3 October 1990.

On that date, the German Democratic Republic ceased to exist as a separate state and its territory joined the Federal Republic of Germany under the Unification Treaty. The five re-established eastern Länder—Brandenburg, Mecklenburg-Vorpommern, Saxony, Saxony-Anhalt and Thuringia—became part of the federal republic, along with reunited Berlin.

The date followed months of fast-moving political change. East Germany held its first free parliamentary election on 18 March 1990, monetary union with West Germany began on 1 July, and the Unification Treaty was signed on 31 August. At midnight on 3 October, the legal accession took effect and the flag of the reunited Germany was raised in Berlin.

The date is commemorated annually as German Unity Day, Germany’s national holiday. The fall of the Berlin Wall on 9 November 1989 began the process but did not itself reunify the country. Likewise, 1 July marked economic and monetary union, not political reunification, while 18 March was the date of East Germany’s first free election.