Contents
- Maa-alused (Estonian) – 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, claw-like fingernails
- Maha-pudma (Hindu) – Giant elephant that holds up the world
- Mahuika (Māori) - Māori fire goddess
- Mairu (Basque) – Megalith-building giant
- Mājas gari (Latvian) – 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) – Spirit of the hunt
- Mami Wata (Africa and the African diaspora) – Supernaturally beautiful water spirits
- Mamuna (Slavic) – Demoness or fairy
- Manananggal (Philippine) – Vampires that sever their torsos from their legs to fly around
- Mandi (Medieval bestiaries) – Humanoid with a forty-year lifespan
- Mandrake (Medieval folklore) – Diminutive humanoid plant
- Manes (Roman) – Ancestral spirits
- Mannegishi (Cree) – Little people with six fingers and no noses
- Manticore (Persian) – Lion-human-scorpion hybrid
- Mapinguari (Brazilian) – Giant sloth
- Mara (Scandinavian folklore) – Female night-demon
- Marabbecca (Italian folklore) – Malevolent water spirit
- Mare (Germanic and Slavic folklore) – Malicious entity which causes or appears in bad dreams
- Mareikura (Tuamotu) – Attendant of Kiho-tumu, the supreme god
- Mares of Diomedes (Greek) – Man-eating horses
- Marid (Arabian) – Jinn-associated fortune tellers
- Marmennill (Norse) – Mermen with prophetic abilities
- Maro deivės (Lithuanian) – Disease spirits
- Marozi (Kenya) – Lion-leopard hybrid
- Maski-mon-gwe-zo-os (Abenaki) – Shapeshifting toad spirit
- Matagot (French) – Spirit that takes animal form, usually that of a black cat
- Matsya (Hindu) – First Avatar of Vishnu in the form of a half-fish and half-man
- Mavka (Slavic) – Female forest spirit
- Mayura (Hindu) – Peacock spirit
- Mazzikin (Jewish) – Invisible, malevolent spirit
- Mbói Tu'ĩ (Guaraní) – Snake-parrot hybrid
- Mbwiri (Central Africa) – Possessing demon
- Medusa (Greek) – Female human-serpent hybrid (Gorgon) with numerous snake heads
- Melek Taus (Yazidi) – Divine bird
- Meliae (Greek) – Ash tree nymph
- Melusine (Medieval folklore) – Female water spirit, with the form of a winged mermaid or serpent
- Menehune (Hawaiian) – Little people and craftsmen
- Menninkäinen (Finnish) – Little people and nature spirits
- Menreiki (Japanese) – Spiritual creature formed from 66 gigaku masks
- Mephistopheles (German) – Demon or devil
- Merlion (Singapore) – Lion-fish hybrid; the symbol of Singapore
- Mermaid/Merman (multiple cultures) – Human-fish hybrid
- Merlin (English) – Elderly wizard
- Merrow (Irish and Scottish) – Human-fish hybrid
- Metee-kolen-ol (Abenaki) – Ice-hearted wizards
- Mimi (Australian Aboriginal) – Extremely elongated humanoid that has to live in rock crevasses to avoid blowing away
- Minka Bird (Australian Aboriginal) – Death spirit
- Minokawa (Philippine) – Giant swallow
- Min Min Light (Australian) – Mysterious light phenomenon
- Minotaur (Greek) – Human-bull hybrid
- Mintuci (Ainu) – Water spirit
- Mishibizhiw (Ojibwa) – Feline water spirit
- Misi-ginebig (Ojibwa) – Serpentine rain spirit
- Misi-kinepikw (Cree) – Serpentine rain spirit
- Mizuchi (Japanese) – Water dragon
- Mogwai (Chinese) – Vengeful ghost or demon
- Mohan (Latin American folklore) – Nature spirit
- Moirai (Greek) – Three fates
- Mokèlé-mbèmbé (Congo) – Water-dwelling creature
- Mokoi (Australian Aboriginal) – Malevolent spirit that kills sorcerers
- Mokorea (Polynesian) – Amphibious humanoid living in the spirit world (underground world)
- Moñái (Guaraní) – Giant snake with antennae
- Mondao (Zimbabwean folklore) – Mermaids/water spirits with long black hair, blood-red eyes, pale skin, and sharp teeth
- 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) – Disembodied spirit
- Morena (Slavic) – Winter spirit
- Morgens (Breton and Welsh) – Water spirits
- Morinji-no-okama (Japanese) – 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) – Shapeshifting badger spirit
- Muldjewangk (Australian Aboriginal) – Water monster
- Multo (Philippine) – Spirit of a deceased person seeking justice or with 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) – Spirits that inspire artists
- Mushusshu (Mesopotamian) – Hybrid beast with long neck and eagle talons
- Musimon (Heraldic) – Sheep-goat hybrid
- Myling (Scandinavian folklore) – Ghosts of unbaptized children
- Myrmecoleon (Medieval bestiaries) – Ant-lion hybrid