God

"Any sufficiently advanced technology is indistinguishable from magic."

- Arthur C. Clarke A God is a supernatural, immortal being believed in or respected by believers. While the existence of one or more Gods remains subject of debate in the real world; Gods and God-like aliens have often being depicted as real entities in science fiction; whilst sometimes non-"supernatural" aliens will make use of superior technology to become worshiped as gods by more primitive cultures. It is also possible to equate the two situations using one of Arthur C. Clarke's laws that states that any sufficiently advanced technology is virtually indistinguishable from magic. The belief in pantheism consist of the idea that the Universe itself is God.

"Real" and Mythological Gods

 * Cthulhu (more correctly a demi-god, as a Great Old One), worshiped by the Spawn of Cthulhu (At the Mountains of Madness) and by Humans (The Call of Chthulhu)
 * Several other entities collectively known as the Great Old Ones (demi-gods) and the Outer Gods (such as Yog-Sothoth and Azathoth) in H. P. Lovecraft's fiction
 * The entity from Robert Sawyer's Calculating God
 * The Firstborn from Arthur C. Clarke's Space Odyssey series
 * The Hitchhiker's Guide to the Galaxy series by Douglas Adams mentions God as a real entity, though noticing that the existence of the Babel Fish provides pretty strong evidence against him, and that he may have already vanished in a puff of logic. Also mentioned in the series are: Almighty Bob (worshiped by the Lamuellans), the Great Green Arkleseizure (worshiped by Jatravartids), Rob McKenna (worshiped by the clouds), and Thor, God of Thunder (in addition to the other Asgardians and Olympian gods)
 * Barry is a worshiped by the Melmacians. Apparently, after their 233rd birthday all Melmacians must chose between becoming ministers for the cult of Barry or becoming outcasts
 * In Valérian and Laureline comics, there are beings which seem to correspond to, and identify themselves as, gods. They live on the mystical world of Hypsis, a planet which is constantly changing location around spacetime. Each small group of gods is responsible for a number of star systems. The three gods responsible for Earth assume the appearance of a middle-aged man, a younger man who claims to be his son, and a clock-like robotic entity. They seemingly represent, respectively: the Abrahamic God, Jesus Christ and the Holy Spirit.
 * The Tosoks worship a female entity known solely as "The God".
 * The Waldahudin are polytheists, believing in numerous gods, including some pretty unusual ones like the God of Alluvial Deposits.
 * The star Sol, seen from the Cheela's homeworld Dragon's Egg in the eponymous book by Robert Forward, was worshiped as an omnipotent god called Bright by the early Cheela civilizations.
 * The Chronomyst from Ascendancy worship a god called Chronos. The Frutmaka, from the same game, worship the god Graveesha, a personification of the black hole that exists near their home planet.
 * Logar is a mystical god worshiped by the Trions of the planet of Sarn, as seen in Doctor Who serial "Planet of Fire".
 * The Mentors worship the god Morgo, as seen in the Doctor Who serial "Mindwarp".
 * Ti is a god worshiped by the Deons, a religious sect of the Tigellans from the Doctor Who story "Meglos".
 * The Goddess of the Delvian Seek is an entity worshipped by the Delvians in Farscape.
 * The Sleestak from Land of the Lost are known to worship a creature, referred by them as a god, which lives in the bottom of a mist-filled pit. Although never seen, only heard, at least one episode contains hints that the monster is indeed supernatural.

Fake Gods

 * An unnamed evil entity at the center of the Milky Way Galaxy claimed to be God in Star Trek V: The Final Frontier.
 * Q also claimed to be God in the Star Trek: The Next Generation episode "Tapestry", where he guides Picard in his near-death experience.
 * The Dalek Emperor was worshiped as a god by Daleks who survived the Last Great Time War in Doctor Who.
 * Yautja were treated as gods by ancient South American cultures on Earth in Alien vs. Predator.
 * Behemecoatyl, the Brain of Brains, is worshiped as a God by all of the Arachnids.
 * The alien known as Magus also claimed to be God in the Space: 1999 episode "New Adam, New Eve", but was revealed to be using technology to fake his powers.
 * The Builders, a mysterious old species which created the Leviathans from Farscape, are worshiped as gods by their creations.
 * Monarch from the Doctor Who serial "Four to Doomsday" believed himself to be God, and planned to go back in time to the creation of the universe to rendezvous with himself.
 * Akhaten is worshiped as a god by the inhabitants of the Sun-singers of Akhet, as seen in the Doctor Who episode "The Rings of Akhaten".
 * The Minotaurs from Doctor Who typically pose themselves as Gods by psychically manipulating, and feeding off, the faith of other creatures.
 * A mutated giant squid called Kroll is worshiped as a god by the Swampies on the moon Delta III from the Doctor Who serial "The Power of Kroll".
 * The Minyans from the Doctor Who serial "Underworld" believed the Time Lords were gods when they first encountered them.
 * The Menoptera from Doctor Who were worshiped as deities by their wingless descendants, the Optera, before the two species were reunited.
 * The artificial intelligence Xoanon is worshipped as a god by Leela's people in the Doctor Who serial "The Face of Evil".
 * The Yargonian leader, Yargo, genuinely believes himself to be a god and is worshiped as one by his people in Jacqueline Susan's Yargo.