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 at the conclusion of Ender's Game. The Shadow series covers the years that Peter serves in this position. 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 character Andrew "Ender" Wiggin about his brother Peter, usually published with The Hive Queen by the same author. Both works are a result of Ender's turning into a Speaker for the Dead after the end of the Formic War.
Earth Awakens - Ukko Jukes
Shadow Series - Peter Wiggin