The Washington Naval Treaty, also known as the Five-Power Treaty, was a treaty signed during 1922 among the major Allies of World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Naval Conference in Washington, D.C. from November 1921 to February 1922 and signed by the governments of the British Empire, United States, France, Italy, and Japan. It limited the construction of battleships, battlecruisers and aircraft carriers by the signatories. The numbers of other categories of warships, including cruisers, destroyers, and submarines, were not limited by the treaty, but those ships were limited to 10,000 tons displacement each.

The Washington Naval Conference was a disarmament conference called by the United States and held in Washington, D.C., from November 12, 1921, to February 6, 1922. It was conducted outside the auspices of the League of Nations. It was attended by nine nations regarding interests in the Pacific Ocean and East Asia. Germany was not invited to the conference, as restrictions on its navy had already been set in the Versailles Treaty. Soviet Russia was also not invited to the conference. It was the first arms control conference in history, and is still studied by political scientists as a model for a successful disarmament movement.