The President of Earth is a theoretical future political office that is common in many science fiction works.
The President of Earth is the president of the entire planet Earth, during a period occurring after all countries of the world have agreed to merge their governments into a single world government. In some science fiction works the office of President of Earth is not the same as leader of all humanity, due to space exploration and human colonization of other planets.
In many cases, the President of Earth is portrayed as occupying an office very similar in style to that of the President of the United States, perhaps alluding to an eventual American takeover of the world, or simply a pro-US bias of the author (ie: the author being more familiar with that office than the office of other world leaders).
Presidents of Earth have been characters in:
In Futurama, Earth President McNeal (voiced by Billy West) is killed by invading Omicronians. In a later episode, Richard Nixon's preserved head is elected the world's president.
In the Red Dwarf novel The Last Human, Nixon's descendant John Milhaus Nixon is President of the World Council.
In the last book of the Animorphs series, The Beginning, Jake Berenson is (jokingly) introduced to the Andalite people as President of Earth.
See also