Which U.S. president was in office when Japan formally surrendered in September 1945?

Harry S. Truman was the U.S. president when Japan formally surrendered in September 1945.

Truman had become president on 12 April 1945, following Franklin D. Roosevelt's death. He therefore led the United States during the final months of the war in Europe and the Pacific, including Japan's announcement of surrender and the formal signing on 2 September.

Truman publicly announced Japan's surrender after the Japanese government accepted the Allied terms. The formal ceremony later took place aboard USS Missouri in Tokyo Bay, where Douglas MacArthur accepted the surrender for the Allied powers.

Roosevelt is sometimes incorrectly named because he was president for most of World War II. However, Roosevelt died before Germany surrendered and before the atomic bombings, Japan's surrender announcement, and the signing ceremony. Truman's presidency covered all of those final events in the Pacific war.