| Name | Source | Type |
|---|---|---|
| Cabal | Destiny franchise | Large, rhinoceros-like humanoids from the planet of Torobatl. Their politics and society are similar to that of Ancient Rome. |
| Caged dude | Adventure Time: Fionna and Cake | |
| Caitian | Star Trek: The Animated Series | Feline humanoid |
| Calamarain | Star Wars | |
| Caleban | Frank Herbert's Whipping Star | invisible telepathic beings who are actually the minds of stars |
| Calcinite | X-COM: Terror from the Deep | |
| Callineans | Star Fleet | Humanoid |
| Calvin | Life | Cephalopod-like |
| Caliban | C. J. Cherryh's Alliance-Union universe | |
| Campbellians | Chōdenji Robo Combattler V | |
| Canaria | Adventure Time: Fionna and Cake | |
| Capelons | Ascendancy | |
| Conductoid | Ben 10 | Black-skinned aliens from planet Teslavorr, Conductoids are cycloptic humanoids with plugs on their fingers, prehensile tail, and antenna on their heads. They have the ability to absorb energy and redirect it as electrical energy. |
| Cascan | Ben 10 | Hailing from planet Cascareau in the Andromeda Galaxy, these aliens are very similar to Orishans, being armored humanoids able to manipulate water. |
| Cardassian | Star Trek | Reptilian Humanoid |
| Carggites | DC Comics Legion of Super-Heroes | |
| Carrionites | Doctor Who | Humanoid |
| Cat | Red Dwarf | Felis Sapiens. Evolved over the course of three million years in deep space, from a domesticated housecat. |
| Catbug | Bravest Warriors | A combination part cat and part ladybug, Catbug simultaneously exists in two dimensions; reality and the See-Through Zone. |
| Cathar | Star Wars | Cat-like humanoid |
| Catkind | Doctor Who | Feline Humanoid. |
| Cat People | The Garfield Show | Feline humanoid. |
| Cat People | Marvel Comics | Feline humanoid |
| Catalyte | Utopia | |
| Catteni | Anne McCaffrey's Catteni Series | |
| Cavalier | Tommy & PJ | |
| Cazare | Ratchet & Clank | |
| Celareon | Conquest: Frontier Wars | |
| Celatid | X-COM: UFO Defense | |
| Celestials | Marvel Comics | |
| Celestialsapien | Ben 10 | Horned humanoids with a body similar to that of a starry night sky from the Forge of Creation, they can warp space, time and reality. However, they are limited by their psyche: their minds are divided into separate personalities that need to agree in order to do even simple tasks, causing them to remain motionless for long periods of time. |
| Centauri | Babylon 5 | Humanoid |
| Centrans | Christopher Anvil's Pandora's Planet stories | Feline humanoids |
| Cerebrocrustacean | Ben 10 | Crab-like aliens from Encephalonus IV with massive heads due to super-sized brains. They are extremely intelligent (their IQ is at one nonillion), though not as smart as Galvans, and can use their enhanced intelligence to perfectly calculate the trajectory of objects, operate complicated machinery, and come up with strategies for combat on the fly, and also generate and manipulate electricity into electric blasts and force fields. |
| Ceti eel | Star Trek II: The Wrath of Khan | bug-like brain parasites from Ceti Alpha V |
| Chaethe | Kathy Tyers's One Mind's Eye | |
| Chalnoth | Star Trek | |
| Chamachies | Ascendancy | |
| Changeling | Star Trek | |
| Chaos | Independence War, aka I-War, and Independence War 2: Edge of Chaos | |
| Charrids | Farscape | Humanoid |
| Chasch | Jack Vance's Planet of Adventure Series | Big headed humanoids divided in subspecies. |
| Chatilian | Battlelords of the 23rd Century | Humanoid |
| Cheblons | Imperium Galactica II: Alliances | |
| Cheela | Dragon's Egg | inhabitants of neutron star |
| Chelonians | Doctor Who novels | |
| Chenjesu | Star Control | Crystalline life-form |
| Cherubs | Homestuck | Cherubs are characterized by their green exoskeleton. |
| Chevanno | Utopia | |
| Chi | C. J. Cherryh's Chanur novels | |
| Chigs | Space: Above and Beyond | |
| Chimera | Resistance: Fall of Man | Reptilian Hybrids between virus and host |
| Chimera Sui Generis | Ben 10 | Green-skinned cephalopodic humanoids from the planet Murray (later renamed Vilgaxia after their leader, galactic warlord Vilgax), who have the ability to turn into monstrous squid-like beings when submerged in water. |
| Chinger | Bill, the Galactic Hero | |
| Chiss | Star Wars | Blue-skinned red-eyed humanoids |
| Chmmr | Star Control | |
| Cho-choi | Jack McDevitt's Infinity Beach | |
| Chronovore | Doctor Who | Universe devourers |
| Chozo | Metroid | Bird-like species. Extremely technologically advanced and spread out across the galaxy. |
| Chronian | Ben 10: Race Against Time | Physically identical to humans. They have vast Time manipulation powers and able to create Energy beams. However, using their time powers weakens them over time, causing them to age faster. |
| Chronomyst | Ascendancy | |
| Chryssalid | X-COM: UFO Defense | |
| Cinnrusskin | James White's Sector General series | |
| Cirronians | Tracker | |
| Cizerack | Battlelords of the 23rd Century | |
| Clairconctlar | Star Control 3 | |
| Clutch Turtles | Liaden universe | |
| Cocytans | The Dig | Furry, bird-like beings trapped in "Spacetime Six", a parallel universe. |
| Coeurl | The Voyage of the Space Beagle by A. E. van Vogt | Similar to a big cat; prehensile tentacles sprouting from shoulders. Feeds on potassium and/or organic phosphorus. |
| Cognocenti | Star Trek | |
| Colatas | Farscape | Humanoid |
| Cole | Adventure Time: Distant Lands | |
| Cole | Tracker | |
| Colonists | The X-Files | |
| Colour out of space | H. P. Lovecraft | |
| Coluans | DC Comics Legion of Super-Heroes | |
| Combine | Half-Life 2 | an alien empire; note: many of the "Combine" seen in the game are actually humans that have been assimilated or collaborate as brutal police troopers. |
| Coneheads | Saturday Night Live | Humanoid with conical heads |
| Control Brains | Invader Zim | The Control Brains assign the Irken race with roles and are the unspoken leaders of the Irken Empire. |
| Coreeshi | Farscape | Humanoid |
| Coridanite | Star Trek | Humanoid |
| Corporal Giroro | Sgt. Frog | |
| Corvallen | Star Trek | Reptilian Humanoid |
| Covenant | Halo | Collective of alien species who are allied with each other, Composed of Grunts, Brutes, Elites, Hunters, Jackals, and Prophets. Religious Hierarchy with intent to destroy the Human Race. |
| Crystals | Raiden | Hi-tech aliens that has control over red crystals with unlimited powers, which are used to power up their weapons and equipment. |
| Cragmite | Ratchet & Clank | |
| Creators | Nexus: The Jupiter Incident | |
| Crescendolls | Interstella 5555 | An alien band, inspired by the Daft Punk song of the same name. |
| Crites | Critters films | carnivorous hairballs |
| Cryons | Doctor Who | A crystalline humanoid race from planet Telos, they cannot survive temperatures above the freezing point, boiling and steaming in said temperatures. |
| Ctarl-Ctarl | Outlaw Star | |
| Cthulhu | Cthulhu Mythos | |
| Cuber | Adventure Time | |
| Cybermen | Doctor Who | Marauding cybernetic life-forms. Originally an alien race driven to conversion by catastrophic climate change, more recently reimagined as assimilated humans. |
| Cybertronians | Transformers | Large robots from planet Cybertron able to change their shape at will into other mechanical constructs, most commonly varying types of vehicles like planes and trucks. Known more commonly as Transformers. |
| Cybyota | Orion's Arm | |
| Cyclons | Metroid series | |
| Cylons | Battlestar Galactica | Sentient robots. Remnants of a civilization of reptilian aliens (also known as Cylons) in the original series, but created by humans in the remake series. Both mechanical and biological flesh-and-blood versions co-exist, with the biological versions in charge. |
| Cynoid | Master of Orion III | |
| Cyrollan | The Journeyman Project |