What was the official document signed by Japan aboard USS Missouri called?

The official document signed by Japan aboard USS Missouri was the Japanese Instrument of Surrender.

This instrument formalized Japan’s capitulation to the Allied powers and ended the fighting of World War II. It was signed in Tokyo Bay on September 2, 1945, by Japanese representatives and Allied representatives from nine governments. The document required Japan to accept the terms of the Potsdam Declaration and ordered its armed forces to stop resistance.

The instrument was not the same as the Potsdam Declaration. The declaration, issued on July 26, 1945, demanded Japan’s surrender and outlined the consequences of continued war. The instrument was the later document through which Japan formally accepted those conditions.

Nor was it the Treaty of San Francisco, the postwar peace treaty that came into force in 1952. The surrender instrument ended active combat and began the occupation, while the later treaty restored Japan’s sovereignty and formally established peace with many Allied countries. Two copies were signed during the ceremony: one for the Allied powers and one for Japan.