The Big Four or the Four Nations refer to the four top Allied powers of World War I and their leaders who met at the Paris Peace Conference in January 1919. The Big Four is also known as the Council of Four. It was composed of Georges Clemenceau of France, David Lloyd George of the United Kingdom, Vittorio Emanuele Orlando of Italy, and Woodrow Wilson of the United States.

The Paris Peace Conference was a set of formal and informal diplomatic meetings in 1919 and 1920 after the end of World War I, in which the victorious Allies set the peace terms for the defeated Central Powers. Dominated by the leaders of Britain, France, the United States and Italy, the conference resulted in five treaties that rearranged the maps of Europe and parts of Asia, Africa and the Pacific Islands, and also imposed financial penalties. Germany, Austria-Hungary, Turkey and the other losing nations were not given a voice in the deliberations; this later gave rise to political resentments that lasted for decades. The arrangements made by this conference are considered one of the great watersheds of 20th-century geopolitical history.