- Cabeiri (Greek) – Smith and wine spirit
- Cacus (Roman) – Fire-breathing giant
- Cadejo (Central America) – Cow-sized dog-goat hybrid
- Cailleach (Scottish) – Divine creator and weather deity hag
- Caipora (Tupi) – Fox-human hybrid and nature spirit
- Caladrius (Medieval Bestiary) – White bird that can foretell if a sick person will recover or die
- Calingi (Medieval Bestiary) – Humanoid with an eight-year lifespan
- Callitrix (Medieval Bestiary) – Apes who always bear twins, one the mother loves, the other it hates
- Calydonian Boar (Greek) – Giant, chthonic boar
- Calygreyhound (Heraldic) – Wildcat-deer/antelope-eagle-ox-lion hybrid
- Camahueto (Chilota) – One-horned calf
- Camazotz (Mayan) – Underworld bat spirit
- Cambion (Medieval folklore) – Offspring of a human and an incubus or succubus
- Campe (Greek) – Dragon-human-scorpion hybrid
- Camulatz (Mayan) – Bird that ate the heads of the first men
- Candileja (Colombian) – Spectral, fiery hag
- Canaima (Guyanese) – Were-jaguar
- Canotila (Lakota) – Little people and tree spirits
- Caoineag (Scottish) – Death spirit (a particular type of Banshee/Bean Sídhe)
- Čhápa (Lakota) – Beaver spirit
- Chareng (Meitei) — Semi-hornbill, semi-human creature
- Căpcăun (Romanian) – Large, monstrous humanoid
- Carbuncle (Latin America) – Small creature with a jewel on its head
- Cath Palug (Welsh) – Monstrous cat
- Catoblepas (Medieval Bestiary) – Scaled buffalo-hog hybrid
- Cat Sidhe (Scottish) – Fairy cat
- Ceasg (Scottish) – Benevolent Scottish mermaids
- Ceffyl Dŵr (Welsh) – Malevolent water horse
- Centaur (Greek) – Human-horse hybrid
- Centicore (Indian) – Horse-Antelope-Lion-Bear hybrid
- Cerastes (Greek) – Extremely flexible, horned snake
- Cerberus (Greek) – Three-headed dog that guards the entrance to the underworld
- Cercopes (Greek) – Mischievous forest spirit
- Cericopithicus (Medieval Bestiary) – Apes who always bear twins, one the mother loves, the other it hates
- Ceryneian Hind (Greek) – Hind with golden antlers and bronze or brass hooves
- Cetus (Greek) - Large sea monster
- Chakora (Hindu) – Lunar bird
- Chalkydri (Apocryphal writings) – Angelic birds
- Chamrosh (Persian) – Dog-bird hybrid
- Chaneque (Aztec) – Little people and nature spirits
- Changeling (European) – Humanoid child (fairy, elf, troll, etc.) substituted for a kidnapped human child
- Charybdis (Greek) – Sea monster in the form of a giant mouth
- Chenoo (Mi'kmaq/Algonquian) – Giant, human-eating ice monsters; former humans who either committed terrible crime(s) or were possessed by evil spirits, turning their hearts to ice
- Chepi (Narragansett) – Ancestral spirit that instructs tribe members
- Cherufe (Mapuche) – Volcano-dwelling monster
- Cheval Mallet (French) – Evil horse who runs away with travelers
- Cheval Gauvin (French) – Evil horse who drowns riders, similar to kelpie
- Church grim (Germanic) – Guardian spirit
- Chibaiskweda (Abenaki) – Ghost of an improperly buried person
- Chichevache – Human-faced cow that feeds on good women
- Chickcharney (Bahamian) – Bird-mammal hybrid
- Chimaera (Greek) – Lion-goat-snake hybrid
- Chindi (Navajo) – Vengeful ghost that causes dust devils
- Chinthe (Burmese) – Temple-guarding feline, similar to Chinese Shi and Japanese Shisa
- Chitauli (Zulu) – Human-lizard hybrid
- Chōchin'obake (Japanese) – Animated paper lantern
- Chol (Biblical mythology) – Regenerative bird
- Chollima (Korean) – Supernaturally fast horse
- Chonchon (Mapuche) – Disembodied, flying head
- Choorile (Guyanese) – Ghost of a woman that died in childbirth
- Chromandi (Medieval Bestiary) – Hairy savage with dog teeth
- Chrysaor (Greek) – Giant son of the gorgon Medusa
- Chrysomallus (Greek mythology) – Golden winged ram
- Chukwa (Hindu) – Giant turtle that supports the world
- Chullachaki
- Chupacabra (Latin America) – Cryptid beast named for its habit of sucking the blood of livestock
- Churel (Hindu) – Vampiric, female ghost
- Ciguapa (Dominican Republic) – Malevolent seductress
- Cihuateteo (Aztec) – Ghost of women that died in childbirth
- Cikavac (Serbian) – Bird that serves its owner
- Cinnamon bird (Medieval Bestiaries) – Giant bird that makes its nest out of cinnamon
- Cipactli (Aztec) – Sea monster, crocodile-fish hybrid
- Cipitio (Salvadoran folklore)
- Cirein cròin (Scottish) – Sea serpent
- Coblynau (Welsh) – Little people and mine spirits
- Cockatrice (Medieval Bestiaries) – Chicken-lizard hybrid
- Cofgod (English) – Cove god
- Colo Colo (Mapuche) – Rat-bird hybrid that can shapeshift into a serpent
- Corycian nymphs (Greek) – Nymph of the Corycian Cave
- Cretan Bull (Greek) – Monstrous bull
- Crinaeae (Greek) – Fountain nymph
- Criosphinx (Ancient Egypt) – Ram-headed sphinx
- Crocotta (Medieval Bestiaries) – Monstrous dog-wolf
- The Cu Bird (Mexican) – El Pájaro Cu; a bird
- Cuco (Latin America) – Bogeyman
- Cucuy (Latin America) – Malevolent spirit
- Cuegle (Cantabrian) – Monstrous, three-armed humanoid
- Cuélebre (Asturian and Cantabrian) – Dragon
- Curupira (Tupi) – Nature spirit
- Cu Sith (Scottish) – Gigantic fairy dog
- Cŵn Annwn (Welsh) – Underworld hunting dog
- Cyclops (Greek) – One-eyed giant
- Cyhyraeth (Welsh) – Death spirit
- Cynocephalus (Medieval Bestiaries) – Dog-headed humanoid