Species

Monster High, being a monster-themed franchise, features a huge cast consisting of many different types of monsters. And some humans to round it out, of which most fit the conventions of the horror genre. Below is the entirety of the cast listed by species, with those who are either unknown or unique to the franchise listed as "other".

Please keep two things in mind when reading:
 * Neither this article nor the specific species articles linked to are necessarily fit for reading by a young audience.
 * Characters are primarily grouped the way canon does it, even though canon sometimes conflicts with real-life (sirens vs mermaids). Where canon is silent, real-life conventions are utilized.

Humans

 * Bartleby Farnum
 * Bekka Madden
 * Brett Redding
 * Candace Carver
 * Chad
 * Clair
 * Jackson Jekyll
 * Haylee
 * Van Hellscream
 * Hexiciah Steam
 * Kipling
 * Lilith Van Hellscream
 * Lilith's goons
 * Lou Zarr

Elementals

 * C.A. Cupid
 * Heath Burns
 * Holt Hyde

Frankenstein monsters

 * Viveka Stein
 * Viktor Stein
 * Frankie Stein

Phantoms

 * Rotter
 * Boolittle
 * Operetta
 * The Phantom of the Opera

Water monsters

 * Lagoona Blue
 * Gillington "Gil" Webber
 * Grimmily Anne McShmiddlebopper
 * Honey Swamp

Skeletons

 * Skelita Calaveras
 * G. Reaper
 * D'Eath
 * Skullastic Superintendents

Zombies

 * Ghoulia Yelps
 * Don of the Dead
 * Sloman "Slo Mo" Mortavitch
 * Neighthan Rot (Hybrid)

Mummies

 * Cleo de Nile
 * Nefera de Nile
 * Ramses de Nile
 * Mummy

Vampires

 * Draculaura
 * Dracula
 * Stoker
 * Elissabat
 * Valentine
 * Gory Fangtell
 * Bram Devein
 * Thad

Ghosts

 * Spectra Vondergeist
 * Johnny Spirit
 * Moanatella Ghostier
 * Sirena Von Boo (Hybrid)
 * Sofeara Gorepola
 * BOO-Lu Cerone

Simulacrums

 * Viktor Stein
 * Viveka Stein
 * Frankie Stein
 * Hoodude Voodoo
 * Gingerbread boy

Robots

 * Robecca Steam
 * Scarentino

Werewolves

 * Brocko
 * Clawd Wolf
 * Clawdeen Wolf
 * Clawdia Wolf
 * Dougey
 * Howleen Wolf
 * Romulus

Werecats

 * Catrine DeMew
 * Catty Noir
 * Meowlody
 * Purrsephone
 * Toralei Stripe

Sirens

 * Melody Carver
 * Rider
 * Siren
 * Sirena Von Boo (Hybrid)

Dragons

 * Jinafire Long
 * Sylphia Flapper

Centaurs

 * Archer
 * Avea Trotter (Hybrid)

Invisibles

 * Billy Phaidin
 * Invisi Billy
 * Verizhe
 * Where

Arthropods

 * Bonita Femur (Hybrid)
 * Buzz Wingman
 * Wydowna Spider

Plants

 * Venus McFlytrap
 * Crabgrass

Cyclopes

 * Iris Clops
 * Cy Clops
 * Simon Clops
 * Laboratory assistant

Magicians

 * Casta Fierce
 * Kindergrubber
 * Scary Murphy

Gargoyles

 * Garrott DuRoque
 * Gary
 * Rocco
 * Rochelle Goyle
 * Scary Stone

Gorgons

 * Deuce Gorgon
 * Euryale Gorgon
 * Medusa Gorgon
 * Stheno Gorgon
 * Viperine Gorgon

Genies

 * Gigi Grant
 * Whisp

Ogres

 * Lothar
 * Ogrethor

Fae

 * Headless Headmistress Bloodgood
 * Scarah Screams

Other

 * Slug girl
 * Neighthan Rot (Hybrid)
 * Avea Trotter (Hybrid)
 * Bonita Femur (Hybrid)
 * Jackson Jekyll/Holt Hyde
 * Abbey Bominable
 * Andy Beast
 * Clouds
 * Eyera
 * Fawn
 * Twyla
 * Hackington
 * Igor
 * Ygor
 * Irene Maiden
 * Lunch lady
 * Manny Taur
 * Music teacher
 * Perfect Guy
 * Ricky
 * School photographer
 * Tiki