Ernst Rudolf Johannes Reuter (29 July 1889 – 29 September 1953) was the mayor of West Berlin from 1948 to 1953, during the time of the Cold War.

He played a significant role in unifying the divided sectors of Berlin and publicly and politically took a stand against the totalitarianism of the Soviet Union.

From 1931 until 1933, Reuter was the mayor of Magdeburg where he fought lack of housing and jobs due to the economic crisis.

In 1933, with the Nazis now in power, he was forced to resign his positions and was brought to the concentration camp (KZ) Lichtenburg near Torgau.

After the end of World War II, Reuter returned to Berlin, and was elected in 1946 to the Magistrate (governing body) where he oversaw initially the Transportation Department.

In 1947 he was elected Lord Mayor (Oberbürgermeister) of Berlin but in the deepening crisis of the Cold War, the Soviet government withheld their necessary consent.

Reuter's speech in front of the burned-out Reichstag building on 9 September 1948 received wide acclaim, where he faced a crowd of 300,000 and appealed to the world not to abandon Berlin.

As mayor he formed a grand coalition government with the next two largest parties to demonstrate West Berlin's unity.

The airlift saved the city from starvation, and Reuter became only the second German postwar politician (after Konrad Adenauer) to be placed on the cover of Time magazine.

The "Champion of Liberty" series issued by the United States Postal Service in 1959 honored Reuter with two stamps for his role in promoting the ideal of a free Berlin, for his significant efforts to unify the western sectors, assisting with the Berlin Airlift and for publicly taking a stance against the Soviet government.