What was the formal name of the agreement that legally ended Japan’s World War II hostilities?

The formal agreement that legally ended Japan’s World War II hostilities was the Japanese Instrument of Surrender.

The document was signed on September 2, 1945, aboard USS Missouri in Tokyo Bay. It stated that Japan accepted the provisions of the Potsdam Declaration and ordered the unconditional surrender of Japanese armed forces. The instrument took effect at 9:25 a.m. that morning.

The Japanese Instrument of Surrender is distinct from the Potsdam Declaration. The declaration, issued on July 26, 1945, set out Allied terms and demanded Japan’s surrender. The instrument was the later document through which Japanese representatives formally accepted those terms.

It is also different from the San Francisco Peace Treaty, signed in 1951. That treaty formally ended the state of war between Japan and many Allied countries and restored Japan’s sovereignty in 1952. The 1945 instrument ended the fighting; it was not the postwar peace treaty.