The Potsdam Declaration, or the Proclamation Defining Terms for Japanese Surrender, was a statement that called for the surrender of all Japanese armed forces during World War II. On July 26, 1945, United States President Harry S. Truman, United Kingdom Prime Minister Winston Churchill, and Chairman of China Chiang Kai-shek issued the document, which outlined the terms of surrender for the Empire of Japan, as agreed upon at the Potsdam Conference. The ultimatum stated that, if Japan did not surrender, it would face "prompt and utter destruction."

The surrender of the Empire of Japan in World War II was announced by Emperor Hirohito on 15 August and formally signed on 2 September 1945, bringing the war's hostilities to a close. By the end of July 1945, the Imperial Japanese Navy (IJN) had become incapable of conducting major operations and an Allied invasion of Japan was imminent. Together with the United Kingdom and China, the United States called for the unconditional surrender of the Japanese armed forces in the Potsdam Declaration on 26 July 1945—the alternative being "prompt and utter destruction". While publicly stating their intent to fight on to the bitter end, Japan's leaders were privately making entreaties to the publicly neutral Soviet Union to mediate peace on terms more favorable to the Japanese. While maintaining a sufficient level of diplomatic engagement with the Japanese to give them the impression they might be willing to mediate, the Soviets were covertly preparing to attack Japanese forces in Manchuria and Korea in fulfillment of promises they had secretly made to the United States and the United Kingdom at the Tehran and Yalta Conferences.