The diplomatic history of World War II includes the major foreign policies and interactions inside the opposing coalitions, the Allies of World War II and the Axis powers, between 1939 and 1945.

The Atlantic Charter was a statement issued on 14 August 1941 that set out American and British goals for the world after the end of World War II, months before the US officially entered the war. The joint statement, later dubbed the Atlantic Charter, outlined the aims of the United States and the United Kingdom for the postwar world as follows: no territorial aggrandizement, no territorial changes made against the wishes of the people (self-determination), restoration of self-government to those deprived of it, reduction of trade restrictions, global co-operation to secure better economic and social conditions for all, freedom from fear and want, freedom of the seas, abandonment of the use of force, and disarmament of aggressor nations. The charter's adherents signed the Declaration by United Nations on 1 January 1942, which was the basis for the modern United Nations.