Contents
- Maa-alused (Estonian mythology) – Subterranean spirit
- Machlyes (Medieval bestiaries) – Hermaphroditic humanoid
- Macrocephali (Medieval bestiaries) – Giant-headed humanoid
- Madam Koi Koi (West African Mythology ) – Female ghost
- Madremonte (Colombian folklore) – Nature guardian
- Maero (Māori) – Savage, arboreal humanoids
- Magog (English folklore) – Giant protector of London
- Mahaha - Undead humanoids with long fingernails as claws.
- Maha-pudma (Hindu mythology) – Giant elephant that holds up the world
- Mahuika (Māori mythology) - Māori fire goddess
- Mairu (Basque mythology) – Megalith-building giant
- Mājas gari (Latvian mythology) – Benevolent house spirit
- Majitu – in Swahili mythology, shape-shifting spirits that can pass as humans
- Makara (Indian mythology) – Aquatic beings
- Makura-gaeshi (Japanese mythology) – Pillow-moving spirit
- Mallt-y-Nos (Welsh mythology) – Spirit of the hunt
- Mami Wata (Africa and the African diaspora) – Supernaturally beautiful water spirits
- Manananggal (Philippine mythology) – Vampires that sever their torsos from their legs to fly around
- Mandi (Medieval bestiaries) – Humanoid with a forty-year lifespan
- Mandrake (Medieval folklore) – Diminutive, animated construct
- Manes (Roman mythology) – Ancestral spirits
- Mannegishi (Cree) – Little people with six fingers and no noses
- Manticore (Persian mythology) – Lion-human-scorpion hybrid
- Mapinguari (Brazilian mythology) – Giant sloth
- Mara (Scandinavian folklore) – Female night-demon
- Marabbecca (Italian folklore) – Malevolent water spirit
- Mare (Germanic and Slavic folklore) – Malicious entity of dream.
- Mareikura (Tuamotu) – Attendant of Kiho-tumu, the supreme god
- Mares of Diomedes (Greek mythology) – Man-eating horses
- Marid (Arabian mythology) – Jinn associated fortune tellers
- Marmennill (Norse mythology) – Mermen with prophetic abilities
- Maro deivės (Lithuanian mythology) – Disease spirits
- Marozi (Kenya) – Lion hybrid leopard
- Maski-mon-gwe-zo-os (Abenaki mythology) – Shapeshifting toad spirit
- Matagot (French mythology) – Spirit that takes animal form; usually that of a black cat
- Matsya (Hindu mythology) – First Avatar of Vishnu in the form of a half-fish and half-man
- Mayura (Hindu mythology) – Peacock spirit
- Mazzikin (Jewish mythology) – Invisible, malevolent spirit
- Mbói Tu'ĩ (Guaraní mythology) – Snake-parrot hybrid
- Mbwiri (Central Africa) – Possessing demon
- Medusa (Greek mythology) – Serpent-female hybrid (Gorgon) with numerous snake heads
- Melek Taus- biblical bird
- Meliae (Greek mythology) – Ash tree nymph
- Melusine (Medieval folklore) – Female water spirit, with the form of a winged mermaid or serpent
- Menehune (Hawaiian mythology) – Little people and craftsmen
- Menninkäinen (Finnish mythology) – Little people and nature spirits
- Mephistopheles
- Merlion (Singapore) – Combination of a lion and a fish, the symbol of Singapore
- Mermaid/Merman (multiple cultures) – Human-fish hybrid
- Merlin (English mythology) – Elderly wizard
- Merrow (Irish mythology and Scottish) – Human-fish hybrid
- Metee-kolen-ol (Abenaki mythology) – Ice-hearted wizards
- Mimi (Australian Aboriginal mythology) – Extremely elongated humanoid that has to live in rock crevasses to avoid blowing away
- Minka Bird (Australian Aboriginal mythology) – Death spirit
- Minokawa (Philippine) – Giant swallow
- Minotaur (Greek mythology) – Human-bull hybrid
- Mishibizhiw (Ojibwa) – Feline water spirit
- Misi-ginebig (Ojibwa) – Serpentine rain spirit
- Misi-kinepikw (Cree) – Serpentine rain spirit
- Mizuchi (Japanese mythology) – Water dragon
- Mogwai (Chinese mythology) – Vengeful ghost or demon
- Mohan (Latin American folklore) – Nature spirit
- Moirai (the fates)
- Mokèlé-mbèmbé (Congo) – Water-dwelling creature
- Mokoi (Australian Aboriginal mythology) – Malevolent spirit that kills sorcerers
- Mokorea (Polynesian mythology) – Amphibious humanoid living in the spirit world (underground world)
- Moñái (Guaraní mythology) – Giant snake with antennae
- Monocerus (Medieval bestiaries) – One-horned stag-horse-elephant-boar hybrid, sometimes treated as distinct from the unicorn
- Mono Grande (South America) – Giant monkey
- Monopod (Medieval bestiaries) – Dwarf with one giant foot
- Mooinjer veggey (Manx folklore) – Nature spirit
- Moon rabbit (Far Eastern folklore) – Legendary animal
- Mora (Slavic mythology) – Disembodied spirit
- Morgens (Breton and Welsh mythology) – Water spirits
- Morinji-no-okama (Japanese mythology) – Animated tea kettle
- Mormolykeia (Greek) – Underworld spirit
- Moroi (Romanian) – Vampiric ghost
- Mo-sin-a (Taiwanese folklore) – Mountain demon
- Moss people (Continental Germanic mythology) – Little people and tree spirits
- Mothman (American folklore) – Large grey winged humanoid with glowing red eyes
- Mugwump (Canadian folklore) – Fish-like lake monster
- Mujina (Japanese mythology) – Shapeshifting badger spirit
- Muldjewangk (Australian Aboriginal mythology) – Water monster
- Multo (Philippine mythology) – Spirit of a deceased person seeking justice or has unfinished business
- Mummy (Egyptian) – Undead creature who revives
- Muma Pădurii (Romanian folklore) – Forest-dwelling hag
- Mungoon-Gali (Australian Aboriginal) – Giant goanna
- Muscaliet (Medieval bestiaries) – Hare-squirrel-boar hybrid that has an intense body heat
- Muse (Greek mythology) – Spirits that inspire artists
- Mushusshu (Mesopotamian mythology)
- Musimon (Heraldic) – Sheep-goat hybrid
- Myling (Scandinavian folklore) – Ghosts of unbaptized children
- Myrmecoleon (Medieval bestiaries) – Ant-lion hybrid