What was the 1945 Allied ultimatum that called for Japan's surrender called?

The 1945 Allied ultimatum that called for Japan's surrender was the Potsdam Declaration.

The declaration was issued on July 26, 1945, by the United States, the United Kingdom, and China. It outlined the terms for ending the war with Japan and demanded the unconditional surrender of all Japanese armed forces. It warned that refusal would bring “prompt and utter destruction.”

The document followed discussions at the Potsdam Conference near Berlin. It stated that Japan's military forces would be disarmed and that Japanese sovereignty would be limited to the four main islands and other islands designated by the Allies.

The Soviet Union did not initially sign the declaration because it was still neutral toward Japan. It agreed to adhere to it on August 8, the same day it declared war. Japan eventually accepted the declaration through Hirohito's August 15 broadcast.