In the popularly acclaimed Ender's Game and Shadow series by Orson Scott Card, the Hegemon is the ruler of the planet. Even though the planet is still divided into countries, the Hegemon has power over them all.
Peter Wiggin, Ender Wiggin's brother becomes the Hegemon in the Shadow series. In the novel, the position of Hegemon was the political leader of Earth. The Hegemon, along with the positions of Polemarch (responsible for the International Fleet of space warships), and the Strategos (responsible for the overall command of solar system defense), was one of the three most powerful people alive. The defeat of the Formics by Ender changed this position. Bean was given the title of Strategos by Peter Wiggin after he assumed the Hegemonship.
The Hegemon is also the title of a fictional book written by Card in the same series, usually sold coupled with The Hive Queen.