What was the formal document that legally recorded Japan’s 1945 capitulation called?

The formal document that recorded Japan’s 1945 capitulation was called the Japanese Instrument of Surrender. It was signed aboard the USS Missouri in Tokyo Bay on September 2, 1945.

An instrument of surrender is a document by which a state or military force formally accepts defeat and the conditions imposed by its opponents. Japan’s instrument stated that the Japanese government accepted the provisions of the Potsdam Declaration and ordered Japanese forces to cease resistance.

The document was signed in two versions: one for the Allied powers and one for Japan. Mamoru Shigemitsu signed for the Japanese government, and Yoshijirō Umezu signed for Imperial General Headquarters. General Douglas MacArthur then accepted the surrender on behalf of the Allies.

The Instrument of Surrender should not be confused with the Potsdam Declaration. The declaration was the Allied statement of surrender terms issued in July; the instrument was Japan’s formal acceptance of those terms. The later Treaty of San Francisco, signed in 1951, was a separate peace treaty.