The Axis powers (German: Achsenmächte, Italian: Potenze dell'Asse, Japanese: 枢軸国 (Sūjikukoku^?)), also known as the Axis alliance, Axis nations, Axis countries, or just the Axis, was the alignment of nations that fought in the Second World War against the Allied forces. The alliance began in 1936 when Germany signed treaties with Italy and Japan. The "Rome-Berlin Axis" became a military alliance in 1939 under the Pact of Steel, with the Tripartite Pact of 1940 leading to the integration of the military aims of Germany and its two treaty-bound allies. At their zenith during World War II, the Axis powers presided over empires that occupied large parts of Europe, Africa, East and Southeast Asia, and islands of the Pacific Ocean. The war ended in 1945 with the defeat of the Axis powers and the dissolution of the alliance. Like the Allies, membership of the Axis was fluid, with nations entering and leaving over the course of the war.

The term "axis" is believed to have been first coined by Hungary's fascist prime minister Gyula Gömbös, who advocated an alliance of Germany, Hungary, and Italy. He worked as an intermediary between Germany and Italy to lessen differences between the two countries to achieve such an alliance. Gömbös' sudden death in 1936 while negotiating with Germany in Munich and the arrival of Kálmán Darányi, a non-fascist successor to him, ended Hungary's initial involvement in pursuing a trilateral axis. The lessening of differences between Germany and Italy led to the formation of a bilateral axis.