Nine Allied nations signed the Japanese Instrument of Surrender besides Japan. The signatories represented the United States, China, the United Kingdom, the Soviet Union, Australia, Canada, France, the Netherlands, and New Zealand.
General Douglas MacArthur signed first for the Allied powers, followed by Fleet Admiral Chester W. Nimitz for the United States. Representatives of the other Allied nations then added their signatures. Japan’s representatives signed before the Allied representatives completed the document.
The number can be miscounted because the ceremony included many military personnel and ships from additional countries. The question refers specifically to governments whose designated representatives signed the instrument. Japan’s two principal signatories were Foreign Minister Mamoru Shigemitsu and General Yoshijirō Umezu.