President of Five Worlds was a political title created by Thrackan Sal-Solo during his second rise to power in 40 ABY. It was briefly the highest executive governmental position for the entire Corellian system.
Having previously been elected Head of State of Corellia, and managing to also become Minister of War for the entire system, Thrackan managed to oust Five World Prime Minister Denjax Teppler from power by unknown means. He then declared himself President of Five Worlds and remained so until his assassination by Boba Fett, Mirta Gev, and Han Solo.
After Thrackan's death, Dur Gejjen took his place in executive power for both the planet of Corellia and the Corellian system as a whole, abolishing the office of President of Five Worlds and reverting to the title Five World Prime Minister.
In Legacy of the Force: Betrayal, it was hinted that Thrackan would attempt to become Five World Prime Minister by killing or toppling Denjax Teppler. But, in Legacy of the Force: Bloodlines, mention is made neither of Teppler nor the Prime Minister position, and he is still listed as being "Head of State." However, he is also called "President" and referred to as the head of the full Corellian government. Presumably this was the result of editing errors as well as due to Bloodlines having been finished before Betrayal. These errors were retconned near the beginning of Legacy of the Force: Tempest when it was stated that Thrackan had declared himself President of Five Worlds in addition to his position as Head of State of Corellia.