A superpower is a state with a dominant position in international relations and is characterised by its unparalleled ability to exert influence or project power on a global scale. This is done through the means of both military and economic strength, as well as diplomatic and soft power influence.

Traditionally, superpowers are pre-eminent among the great powers (i.e. as the United States is today). The term first applied to the British Empire, the United States and the Soviet Union. However, following World War II and the Suez Crisis in 1956, the United Kingdom's status as a superpower was greatly diminished; for the duration of the Cold War the United States and the Soviet Union came to be generally regarded as the two remaining superpowers, dominating world affairs.

At the end of the Cold War and the collapse of the Soviet Union in 1991, only the United States of America appeared to fulfil the criteria of being a world superpower.

Alice Lyman Miller defines a superpower as "a country that has the capacity to project dominating power and influence anywhere in the world, and sometimes, in more than one region of the globe at a time, and so may plausibly attain the status of global hegemony.