- Jersey Devil
- Jesús Aceves
- Jet Jaguar
- Jewish Demonology
- Jiang Shi
- Jiaolong
- Jigoku
- Jigsaw
- Jikininki
- Jimmy Squarefoot
- Jinmenju
- Jinn
- Jinnii
- Jinshin-uwo
- Jiutou Zhiji Jing
- Jo-Jo the Dog-Faced Boy
- Joachim Kroll
- Joan the Wad
- Jodu māte
- Jogah
- John Edward Robinson
- John George Haigh
- John Reginald Halliday Christie
- John Wayne Gacey
- John Wayne Gacy
- John Wayne Glover
- Joint-eater
- Joint snake
- Jorge Luis Borges
- Jormungand
- Jormungandr
- Jorogumo
- Joseph Paul Franklin
- Joseph Vacher
- Josephene Myrtle Corbin
- Jotun
- Juan Baptista dos Santos
- Juan Corona
- Jubokko
- Julia Pastrana
- Jumbie
- Jungli admi
- Juraci and Nadir Climerio de Oliveria
- Jure Grando
- Jyaki
- Jörmungandr
- Jörmungandr,
- Jé-rouges
- Jörmungandr
- Jötunn
- J’Ba FoFi
- K'n-yan
- Kaaiman
- Kabouter
- Kaboutermannekin
- Kachina
- Kaiju
- Kaitabha
- Kakundakári
- Kalanoro
- Kalayavan
- Kali
- Kali (demon)
- Kallikantzaroi
- Kallikantzaros
- Kamacuras
- Kamadhenu
- Kamaitachi
- Kameosa
- Kami-kiri
- Kamikui
- Kanaima
- Kanko
- Kap Dwa
- Kappa
- Kappa-Mythological Creatures
- Kapre
- Kaptar
- Karakasa
- Karakoncolos
- Karakondjul
- Karkadann
- Karl Denke
- Karl Grossmann
- Kartik
- Karuka
- Kasa-obake
- Kashabo
- Kashima Reiko
- Kataw
- Katie King
- Kaukas
- Kee-Boo
- Keelut
- Kegrim
- Keizer Ghidorah
- Kekkai
- Kelpie
- Ker
- Kerakera-onna
- Keres
- Kerit
- Keshi
- Keukegen
- Khala
- Khara
- Khenglong-po
- Khrafstra
- Ki-lin
- Kijimunaa
- Kikimora
- Killmoulis
- Kimeris
- King Arthur
- King Caesar
- King Ghidorah
- King Goldemar
- Kingstie
- Kipsy
- Kirin
- Kiskil-lilla
- Kitsune
- Klabautermann
- Kleidouchos
- Kleine-Levin syndrome
- Kludde
- Klêidouchos
- Knackers
- Knights of Ålleberg
- Knocker
- Knocky-boh
- Knucker
- Koboku-no-kai
- Kobold
- Kobold (Dungeons & Dragons)
- Kodama
- Koka
- Komodo dragon
- Konaki-jiji
- Kongamato
- Kontsodaimonas
- Koril
- Korils
- Kornikaned
- Koro-pok-guru
- Korrigan
- Kpelekpe
- Kraken
- Krampus
- Krao Farini
- Krasue
- Kresnik
- Kroni
- Kubikajiri
- Kuchisake-onna
- Kudlak
- Kui
- Kujata
- Kujuta
- Kukudhi
- Kukuthi
- Kulshedra
- Kuma Lisa
- Kumakatok
- Kumbway
- Kumiho
- Kumonga
- Kun
- Kunal-trow
- Kuntilanak
- Kur
- Kuraokami
- Kurkulla
- Kurotrophos
- Kurukulla
- Kurupira
- Kushtaka
- Kusshii
- Kuyutha
- Kuzuryu
- Kyklope
- Kyklops
- Kylin
- Kymorii
- Kyöpelinvuori
- La Chusa
- La Diablesse
- La Guita Xica
- La Llorona
- La Velue
- Labartu
- Labasu
- Lac Long Quan
- Ladon
- Lady White Snake
- Ladykins
- Lagarfljót Worm
- Lagarfljótsormurinn
- Lahamu
- Lahmu
- Laidly Worm of Spindleston Heugh
- Laima
- Lake Elsinore Serpent
- Lake Murray Monster
- Lake Oymyakon Monster
- Lake Tianchi monster
- Lake Van Monster
- Lake Worth monster
- Lake and sea monsters
- Lake monster
- Laloo Ramparsad
- Lam
- Lamashtu
- Lamassu
- Lamb
- Lamb tree
- Lambana
- Lambton Worm
- Lamhoyo
- Lamia
- Lamia (monster)
- Lammasu
- Lampades
- Lampijerovic
- Lamya
- Landvættir
- Lange Wapper
- Langsuir
- Langsuyar
- Lapithe
- Lare
- Lariosauro
- Larva
- Lauma
- Laurell K. Hamilton
- Lausks
- Lavanasura
- Lavandière de la nuit
- Lavellan
- Lazarus and Joannes Baptista Colloredo
- Leanan Sidhe
- Leanashe
- Leatherface
- Legend
- Legendary creatures of the Argentine Northwest region
- Legion
- Leimakid
- Leimenide
- Leonard
- Leopard man
- Lepke
- Leppalúði
- Leprechaun
- Leraje
- Lernaean Hydra
- Les lavandières de la nuit
- Leshi
- Leshy
- Lesley Whittle
- Lesovik
- Lestat de Lioncourt
- Leszi
- Leucrocotta
- Leucrota
- Leurre
- Leviathan
- Leyak
- Lhiannan Shee
- Lhiannnan-Shee
- Li Ching-Yun
- Liath Macha
- Lich
- Liches
- Liderc
- Liengu
- Light Elf
- Lil Tetrax
- Lilit
- Lilith
- Lilitu
- Lilu
- Limnade
- Lincoln's ghost
- Lindworm
- Link
- Linton Worm
- Liou Seng-Sen and Liou Tang-Sen
- List of Asuras
- List of Children of Oceanus
- List of Japanese demons
- List of Oceanids
- List of Potamoi
- List of lake monsters
- List of serial killers
- List of specific demons and types of demons
- List of templates
- Little Blue Man
- Lizard Man of Scape Ore Swamp
- Ljubljana dragon
- Llamhigyn Y Dwr
- Llorona
- Loa
- Lobizon
- Loch Ness monster
- Loffa
- Loireag
- Loki
- Long Nu
- Longinus
- Longma
- Longwitton dragon
- Loogaroo
- Lordi
- Lords of the Nine
- Los Indios De Las Augas
- Lotan
- Lotti and Rosemarie Knaak
- Lou Carcolh
- Louis Gaufridi
- Louise Capeau
- Louise L
- Louise L.
- Loup-Garou
- Loup Garou
- Loveland frog
- Loveless Place
- Lucian Staniak
- Lucifer
- Lucio and Simplicio Godina
- Lugarhoo
- Lugat
- Luigi Chiatti
- Luis Garavito
- Luison
- Lukwata
- Luridan
- Lusca
- Ly Erg
- Lycanthrope
- Lycaon
- Lympago
- MIB
- Ma-Mian
- Maahiset
- Maal