President of Earth

From Memory Alpha, the free Star Trek reference

The President of Earth was a fictional character in The Adventures of Captain Proton holoprogram. In order to communicate with photonic lifeforms on the holodeck believing the simulation was real and only photonic lifeforms were real, The Doctor took on this role and convinced them to help Captain Proton to defeat Doctor Chaotica and his army of evil. (VOY: "Bride of Chaotica!")

[edit] Apocrypha

In the novel Starfleet: Year One, it is a real position, and around 2161 was held by Lydia Littlejohn.