Atlantic Charter, joint declaration by the United States and Great Britain, issued during World War II (although before the United States had entered the war), expressing certain common principles in their national policies to be followed in the post-war period. The declaration was made and signed on August 14, 1941, by President Franklin D. Roosevelt and Prime Minister Sir Winston Churchill after a series of conferences aboard a warship in the North Atlantic off the coast of Newfoundland.

The two leaders declared that the United States and Great Britain sought no territorial, or any other, aggrandizement from the war. They proclaimed the right of all peoples to choose their own form of government and not to have boundary changes imposed on them. The right of all nations—victors and vanquished—to have access to the Earth's natural resources was also recognized, as was the desirability of economic cooperation among nations and improved living conditions for working people. The charter expressed the hope that, after the defeat of the Nazis, all countries would be able to feel secure from aggression, and that the people of the world would be free from fear and want. It recognized the principle of freedom of the seas, expressed the conviction that humanity must renounce the use of force in international relations, and affirmed the need for disarmament after the expected Allied victory.

At a conference held in Washington, D.C., on January 1, 1942, the 26 governments then at war with the Axis powers declared that they “subscribed to a common programme of purposes and principles embodied in the joint declaration...known as the Atlantic Charter”. The statement embodying this adherence to the charter, called the United Nations Declaration, was later signed by most of the free nations of the world and formed the basis of the United Nations organization established at San Francisco in April-June 1945.