- Obsession: Tales of Irresistible Desire
- Obtuse
- Occasional Demons
- Occult tales
- Occupant
- Occupation
- Oceanear Tales Volume 1
- Oceanfront Dining
- Oceans Of Death
- October
- October Ballet
- October Fury
- October Midnight
- October Nights 2
- October Nights 3
- October Nights: 31 Tales of Haunting & Halloween
- October Roses
- October Tales: Seven Creepy Tales
- October's Gone
- Octopocalypse
- Ocularity
- Oculus - Das Ende der Zeit
- Oculus - Im Auge des Sturms
- Oczy pełne strachu
- Od and Ed
- Odakint sötétebb
- Odd Apocalypse
- Odd Ends: A Double Shot of Horror
- Odd Habit: A Short Story
- Odd Hours
- Odd Interlude
- Odd Thomas
- Odds And Ends: A Dark Collection
- Ode to Classics
- Odessa Incident
- Odiabili resti
- Odio nella terra, tarli nella testa
- Odio volare
- Odium - 100 Horrorgeschichten
- ODIUM - 100 Horrorgeschichten
- Odyssées chimériques
- Oeuvres (Traduites Par Charles Baudelaire)
- Of A Feather
- Of Blood and Politics
- Of blood… Without love - Tome 2
- Of Boardwalks and Bison
- Of Dark and Yesterday
- Of Flesh & Blood
- Of Love and Vampires
- Of Machines and Men
- Of Masques and Martyrs
- Of Mist and Shadow
- Of Moons and Monsters
- Of Our Very Own
- Of Pagan Gods and other tales
- Of Secrets and Sound
- Of Sudden Origin Part 1: The Exodus Is Over
- Of the Dead and Dying: Undead Advantage II
- Of the Shadows Own Accord (The Green and Pleasant Land, Volume 3)
- Of the Undead: A Six-Story Bundle
- Of Things Beneath
- Ofelia
- Off the Beaten Path
- Off the Leash
- Off The Rails
- Offbeat: Uncollected Stories
- Offerings
- Og-Grim-Dog and The War of The Dead
- Og-Grim-Dog: Ogre's End Game
- Ogan the Chosen One
- Oggi non vado a scuola
- Oh my God!
- Oh!Rorscope
- Oh, Deadly Night
- Ohne Gesicht
- Oink
- Ojeando la Hoja
- Ojos de fuego
- Oke of Okehurst - or, A Phantom Lover
- Okkulte & kuriose Rituale
- Oktoberoffer
- Októberi vidék
- Ol George
- Olalla
- Olalla (Cryptofiction Classics - Weird Tales of Strange Creatures)
- Old Bone Dog
- Old Bones and New Flesh
- Old Bones Secret Rain
- Old Church Ghosts - Special Edition
- Old Church Ghosts- The Unseen Version
- Old Church Ghosts-Special Edition
- Old Fears
- Old Friends
- Old George
- Old Gooseberry
- Old Granny Maple
- Old Hollow
- Old Jack's Tale
- Old Lady Ketchel's Revenge: The Slaughter Minnesota Horror Series Book 1
- Old Lady Mary
- Old MacDonald Had a Farm: A Horror Story
- Old Man Scratch
- Old Man's Beard
- Old Mill Road
- Old Nick
- Old Nick's Imp (a holiday flash fiction story)
- Old Palace
- Old Shock
- Old Spice Love Knot - A Nova Scotia Ghost Story
- Old World (The Green and Pleasant Land, Volume 1)
- Old Wounds
- Olgolgen
- Olhos vermelhos
- Olhos Vermelhos