What was the name of the Japanese document signed on September 2, 1945?

The document signed on September 2, 1945, was the Japanese Instrument of Surrender.

This printed agreement formalized Japan’s capitulation and ended the hostilities of World War II. It was signed aboard USS Missouri in Tokyo Bay by representatives of Japan and nine Allied governments: the United States, China, the United Kingdom, the Soviet Union, Australia, Canada, France, the Netherlands, and New Zealand.

The instrument required Japan to accept the provisions of the Potsdam Declaration and ordered Japanese forces to cease active resistance. Mamoru Shigemitsu signed for the Japanese government, followed by General Yoshijiro Umezu for Imperial General Headquarters. Douglas MacArthur and the other Allied representatives then signed.

The instrument is not the same thing as the later peace treaty. The Treaty of San Francisco, signed in 1951 and effective in 1952, formally restored peace between Japan and many Allied countries and ended the occupation framework. The 1945 instrument instead marked the immediate military surrender and termination of wartime operations.