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 is most notable for his stance during the Cold War in Berlin.
During the Soviet-imposed Berlin Blockade (1948/49), the western part of city was sustained by the Berlin airlift that was established by the American Military Governor, Lucius D. Clay.
In response to the threat, the citizens in the western sectors had to come together.
Ernst Reuter became their spokesman and leader, a symbolic figure of the "Free" Berlin.
Memorable is Reuter’s speech in front of the burned-out Reichstag building on 9 September 1948, facing a crowd of 300,000 where he appealed to the world not to abandon Berlin.
In the election that was conducted in the western part of Berlin two months later, his popularity gave the SPD the highest win with 64.5% ever achieved by any party in a free election in Germany.
As mayor he formed a grand coalition government with the next two largest parties to demonstrate West Berlin’s unity.
Reuter's appeal to the West did not go unheard.
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.
He was titled "Herr Berlin".

When the new Berlin State Constitution became effective for West Berlin, Reuter was re-elected and on 18 January 1951, became what was now called the Governing Mayor (Regierender Bürgermeister) of West Berlin.
He served in this function until his death.

Under his aegis, the Free University of Berlin was founded, as the University of Berlin was in the Soviet sector and under communist rule.
In 1953 Reuter established the "Bürgermeister-Reuter-Stiftung" (Mayor Reuter Foundation) to assist refugees coming to West-Berlin.

A few months after the uprising of 17 June 1953 in East Berlin, Reuter died from a sudden heart attack in West Berlin.
He was 64 years old.
His funeral was attended by more than 1 million people and he was honored with an Ehrengrab (honorary grave) in the Waldfriedhof Zehlendorf.
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 is most notable for his stance during the Cold War in Berlin. During the Soviet-imposed Berlin Blockade (1948/49), the western part of city was sustained by the Berlin airlift that was established by the American Military Governor, Lucius D. Clay. In response to the threat, the citizens in the western sectors had to come together. Ernst Reuter became their spokesman and leader, a symbolic figure of the "Free" Berlin. Memorable is Reuter’s speech in front of the burned-out Reichstag building on 9 September 1948, facing a crowd of 300,000 where he appealed to the world not to abandon Berlin. In the election that was conducted in the western part of Berlin two months later, his popularity gave the SPD the highest win with 64.5% ever achieved by any party in a free election in Germany. As mayor he formed a grand coalition government with the next two largest parties to demonstrate West Berlin’s unity. Reuter's appeal to the West did not go unheard. 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. He was titled "Herr Berlin".
When the new Berlin State Constitution became effective for West Berlin, Reuter was re-elected and on 18 January 1951, became what was now called the Governing Mayor (Regierender Bürgermeister) of West Berlin. He served in this function until his death.
Under his aegis, the Free University of Berlin was founded, as the University of Berlin was in the Soviet sector and under communist rule. In 1953 Reuter established the "Bürgermeister-Reuter-Stiftung" (Mayor Reuter Foundation) to assist refugees coming to West-Berlin.
A few months after the uprising of 17 June 1953 in East Berlin, Reuter died from a sudden heart attack in West Berlin. He was 64 years old. His funeral was attended by more than 1 million people and he was honored with an Ehrengrab (honorary grave) in the Waldfriedhof Zehlendorf.
Ernst Reuter