- La-bar-tu [ broken anchor ] (Assyrian) – Disease demon
- Labbu (Akkadian) – Sea snake
- Lady midday (Slavic) – Sunstroke spirit
- Ladon (Greek) – Dragon guarding the golden apples of the Hesperides
- Laelaps (Greek) – Enchanted dog that always caught his prey
- Laestrygonians (Greek) – Anthropophagic giants
- Lakanica (Slavic) – Field spirit
- Lake monster (Worldwide) – Gigantic animals reported to inhabit various lakes around the world
- Lakhey (Nepalese) – Demon with fangs
- La Llorona (Latin America) – Death spirit associated with drowning
- Lamassu (Akkadian and Sumerian) – Protective spirit with the form of a winged bull or human-headed lion
- Lambton Worm (English) – Giant worm
- Lamia (Greek) – Child-devouring monster with an upper body of a woman and a tail of a snake
- Lamiak (Basque) – Water spirit with duck-like feet
- La Mojana (Colombian) – Shapeshifting, female water spirit
- Lampades (Greek) – Underworld nymph
- Landvættir (Norse) – Nature spirits
- Langmeidong (Meitei mythology) – Semi human, semi hornbill creature
- Lares (Roman) – House spirit
- La Sayona (Venezuela) – Female ghost that punishes unfaithful husbands
- La Tunda (Colombian) – Nature spirit that seduces and kills men
- Lava bear – Miniature bear thought to inhabit the lava beds of south central Oregon
- Laukų dvasios (Lithuanian) – Field spirit (Not mythology)
- Lauma (Baltic) – Sky spirit
- Lavellan (Scottish) – Gigantic water rat
- Leanan sidhe (Celtic) – Fairy lover
- Leanashe (Irish) – Possessing spirit or vampire
- Leimoniads (Greek) – Meadow nymph
- Leokampoi (Etruscan) – Fish-tailed lion
- Leontophone (Medieval Bestiary) – Tiny animal poisonous to lions
- Leprechaun (Irish) – Cobbler spirit
- Leszi (Slavic) – Tree spirit
- Leuce (Greek) – White poplar tree nymph
- Leucrota (Medieval Bestiary) – Crocotta-lion hybrid
- Leviathan (Jewish) – Sea monster seen in Job 41
- Leyak (Balinese) – Anthropophagous flying head with entrails
- Libyan Aegipanes (Medieval Bestiaries) – Human-horse hybrid
- Libyan Satyr (Medieval Bestiaries) – Human-goat hybrid
- Lidérc (Hungary) – Magical chicken that transforms into a humanoid
- Lietuvēns (Latvia) - Soul of a murdered person
- Lightning Bird (Southern Africa) – Magical bird found at sites of lightning strikes
- Likho (Slavic) – One-eyed hag or goblin
- Lilin (Jewish) – Night-demoness
- Lilitu [ broken anchor ] (Assyrian) – Winged demon
- Limnades (Greek) – Lake nymph
- Lindworm (Germanic) – Dragon
- Ljósálfar (Norse) – Sunlight spirits; the Light Elves
- Ljubi (Albanian) – Demoness
- Llamhigyn Y Dwr (Welsh) – Frog-bat-lizard hybrid
- Loch Ness Monster (Scottish) – Serpentine sea monster
- Loki (Norse mythology) – God of night
- Lo-lol (Abenaki) – Hideous monster
- Lóng – Chinese dragon
- Long Ma (Chinese) – Dragon-horse hybrid
- Loogaroo (French America) – Shapeshifting, female vampire
- Lou Carcolh (French) – Snake-mollusk hybrid
- Loup-garou (French) – Werewolf
- Loveland frog (American Folklore) (Ohio) – Cryptid, Humanoid Frog
- Lubber fiend (English) – House spirit
- Luduan (Chinese) – Truth-detecting animal
- Lugat (Albanian) – Vampire
- Lui-kong-tsiau (Taiwanese) – Thunderbird
- Luison (Guaraní) – Werewolf | Cadaver-eating dog
- Lusca – Sea Monster
- Lutin (French) – Amusing goblin
- Lyngbakr
- Lynx (Medieval Bestiaries) – Feline guide spirit