President Gaius was supreme leader of Ape City. Dr. Zaius was answerable to him but the governing orangutan elite generally agreed on matters of faith and protection of ape order. Gaius oversaw Taylor's interrogation and found in favour of Zaius. Gaius later died when Taylor activated the Alpha-Omega Bomb which destroyed Earth.
- The earliest movie scripts by Rod Serling retained Boulle's version of the gorilla president and his friendly welcome for 'Thomas' (Taylor). Serling's later revisions were similar, but changed the president's species to orangutan, reflecting a much more stereotypical division of the ape classes.
- The name Gaius was used in the 2011 novel Conspiracy of the Planet of the Apes. Here, the President sympathised with General Ursus' plan to consolidate gorilla power and invade the Forbidden Zone, but insisted the will of the majority should be respected to reject the plan.
- Planet of the Apes Magazine: Planet of the Apes
- Adventures on the Planet of the Apes: Planet of the Apes
- Conspiracy of the Planet of the Apes
- Death of the Planet of the Apes