What was the formal name of the document that ended Japan’s participation in World War II?

The formal document was called the Japanese Instrument of Surrender.

It was the printed agreement that recorded Japan’s capitulation to the Allied powers on September 2, 1945. The document required Japan to accept the terms of the Potsdam Declaration and directed Japanese forces to cease hostilities and surrender.

Representatives signed it aboard USS Missouri in Tokyo Bay. Mamoru Shigemitsu signed for the Japanese government, Yoshijiro Umezu signed for Imperial General Headquarters, and Douglas MacArthur signed for the Allied powers.

An instrument of surrender is different from a peace treaty. It records capitulation and establishes immediate military obligations; it does not necessarily settle every long-term political issue. The later Treaty of San Francisco, signed in 1951, addressed Japan’s postwar peace and sovereignty arrangements.