List of legendary creatures (O)
- Obake (Japanese) â Shapeshifting spirits
- Obariyon (Japanese) â Spook which rides piggyback on a human victim and becomes unbearably heavy
- Obayifo (Ashanti) â Vampiric possession spirit
- Obia (West Africa) â Gigantic animal that serves witches
- Oceanid (Greek) â Nymph daughters of Oceanus
- Odei (Basque) â Storm spirit
- Odin (Norse mythology) â King of Asgard
- Odmience (Slavic) â Changeling
- Og (Jewish) â Giant king of the Amorites
- Ogopogo (Canadian) Canadian Lake Monster
- Ogun (Nigeria) â Iron god for the Yoruba people (South Western Nigeria)
- Ogre (Medieval folklore) â Large, grotesque humanoid
- Oiwa (Japanese) â Ghost of a woman with a distorted face who was murdered by her husband
- Ojáncanu (Cantabrian) â Giant cyclops who embodies evil.
- Ã
Âkami (Japanese) â Spirit wolf of powerful
- Okiku (Japanese) â Spirit of a plate-counting servant girl, associated with the "Okiku-Mushi" worm
- ÃÂksökö (Yakut/Dolgan) â Two or three-headed eagle
- Ã
Âkubi (Japanese) â Death spirit
- Okuri-inu (Japanese) â Dog or wolf that follows travelers at night, similar to the Black dog of English folklore
- Ole-Higue (Guyanese) â Vampiric hag who takes the form of a fireball at night
- Ã
Âmukade (Japanese) â Giant, human-eating centipede that lives in the mountains
- Oni (Japanese) â Large, grotesque humanoid demon, usually having red skin and horns
- Onibi (Japanese) â Spectral fire
- Onikuma (Japanese) â Bear monster with enormous strength that walks upright
- Onmoraki (Japanese) â Bird-demon created from the spirits of freshly dead corpses
- Onocentaur (Medieval Bestiaries) â Human-donkey hybrid
- Onoskelis (Greek) â Shapeshifting demon
- OnryÃ
 (Japanese) â Vengeful ghost that manifests in a physical rather than a spectral form
- Onza (Aztec and Latin American folklore) â Wild cat, possibly a subspecies of cougar
- Oozlum bird (Unknown origin) â Bird that flies backwards
- Ophiotaurus (Greek) â Bull-serpent hybrid
- Opinicus (Heraldic) â Lion-eagle hybrid, similar to a griffin, but with leonine forelimbs
- Opiyel Guabiron (TaÃÂno) â A dog-shaped god that watched over the dead
- Orang Bunian (Malay) â Forest spirit
- Orang Minyak (Malay) â Spectral rapist
- ÃÂrdög (Hungarian) â Shapeshifting demon
- Oread (Greek) â Mountain nymph
- Ork (Tyrolean) â Little people and house spirits
- Orobas (European) â Horse-headed, honest oracle classed as a demon
- Orphan Bird (Medieval Bestiaries) â Peacock-eagle-swan-crane hybrid
- Orthrus (Greek) â Two-headed dog
- Osiris (Hellenized) â God of the dead and the judge of the underworld
- Oshun (Nigeria) â God of love and fertility
- Otso (Finnish) â Bear spirit
- Ouroboros (Worldwide) â Mystic serpent/dragon that eats its own tail
- Ovinnik (Slavic) â Malevolent threshing house spirit
- Owlman (Cornish) â Owl-like humanoid