What was the formal document called that ended hostilities between Japan and the Allies in World War II?

The formal document that ended hostilities between Japan and the Allies was the Japanese Instrument of Surrender.

The instrument was signed aboard USS Missouri in Tokyo Bay on September 2, 1945. It stated that Japan accepted the provisions of the Potsdam Declaration and ordered the unconditional surrender of Japanese armed forces.

Foreign Minister Mamoru Shigemitsu signed for the Japanese government, while General Yoshijiro Umezu signed for Imperial General Headquarters. General Douglas MacArthur and representatives of nine Allied nations then signed on the Allied side.

The Instrument of Surrender should not be confused with a later peace treaty. It ended active hostilities and established Japan’s capitulation, while the Treaty of San Francisco, signed in 1951 and effective in 1952, formally ended the Allied occupation and restored Japan’s sovereignty under postwar terms.