The Treaty of Peace with Japan (commonly known as the Treaty of San Francisco or San Francisco Peace Treaty), between Japan and part of the Allied Powers, was officially signed by 48 nations on September 8, 1951, at the War Memorial Opera House in San Francisco, United States. It came into force on April 28, 1952.

This treaty served to end officially World War II, to end formally Japan's position as an imperial power, and to allocate compensation to Allied civilians and former prisoners of war who had suffered Japanese war crimes. This treaty made extensive use of the UN Charter and the Universal Declaration of Human Rights to enunciate the Allies' goals.

This treaty, along with the Security Treaty signed that same year, is said to mark the beginning of the "San Francisco System"; this term, coined by historian John W. Dower, signifies the effects of Japan's relationship with the United States and its role in the international arena as determined by these two treaties and is used to discuss the ways in which these effects have governed Japan's post-war history.