East Berlin was the name given to the eastern part of Berlin between 1949 and 1990. It consisted of the Soviet sector of Berlin that was established in 1945. The American, British and French sectors became West Berlin, a de facto part of West Germany. Despite its status as part of an occupied city, East Berlin was claimed as the capital of the German Democratic Republic (GDR). From 13 August 1961 until 9 November 1989 East Berlin was separated from West Berlin by the Berlin Wall. The East German government referred to East Berlin simply as "Berlin" or often "Berlin, Hauptstadt der DDR" (Berlin, capital of the GDR). The term "Democratic Sector" was also used until the 1960s. (See also Naming conventions)

The Western Allies (the USA, Great Britain and France) never formally acknowledged the authority of the East German government to govern East Berlin; the official Allied protocol recognized only the authority of the Soviet Union in East Berlin in accordance with the occupation status of Berlin as a whole. The United States Command Berlin, for example, published detailed instructions for U.S. military and civilian personnel wishing to visit East Berlin. In fact, the three Western commandants regularly protested the presence of the East German National People's Army (NVA) in East Berlin, particularly on the occasion of military parades. Nevertheless, the three Western Allies eventually established embassies in East Berlin in the 1970s, although they never recognized it as the capital of the GDR. Treaties instead used terms such as "seat of government."

On 3 October 1990, West and East Germany were reunited, thus formally ending the existence of East Berlin.