List of legendary creatures (M)
- Maa-alused (Estonian mythology) - Subterranean spirit
- Machlyes (Medieval bestiaries) - Hermaphroditic humanoid
- Macrocephali (Medieval bestiaries) - Giant-headed humanoid
- Madremonte (Colombian folklore) - Nature guardian
- Maero (Māori) - Savage, arboreal humanoids
- Magog (English folklore) - Giant protector of London
- Maha-pudma (Hindu mythology) - Giant elephant that holds up the world
- 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
- 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
- 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
- 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
- Merlion (Singapore) - Combination of a lion and a fish, the symbol of Singapore
- Mermaid/Merman (multiple cultures) - Human-fish hybrid
- Merlin (English mythology) - An 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
- Mokèlé-mbèmbé (Congo) - Water-dwelling creature
- Mokoi (Australian Aboriginal mythology) - Malevolent spirit that kills sorcerers
- 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
- 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
- Moss people (Continental Germanic mythology) - Little people and tree spirits
- Mothman (American Folklore) West Virginia Folklore - Large grey winged humanoid with glowing red eyes
- 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
- 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