M
- Mara (Falling Under by Gwen Hayes)
- Mary Shaw (Dead Silence)
- The Manager (Stephen King's The Shining)
- Demon King Maarg (The Riftwar Cycle series)
- Maderas (Disgaea)
- Mariska, the Zombie Queen of Psychedilia (Lollipop Chainsaw)
- Mal'Ganis (Warcraft series)
- Malacoda (Dante's Inferno)
- Malebolgia (Spawn)
- Maledict (Doom 3: Resurrection of Evil)
- Malfegor (Magic: The Gathering)
- Malice (The Demonata)
- Mammon (Umineko no Naku Koro Ni)
- Mama (Mama movie)
- Mancubus (Doom video game series)
- Mannoroth (Warcraft series)
- Majora (The Legend of Zelda: Majora's Mask)
- Marilith (Dungeons & Dragons fantasy game)
- Masselin (Charmed TV series)
- Maxwell's Demon
- Meg Masters (Supernatural TV series)
- Mehrunes Dagon (Elder Scrolls IV: Oblivion)
- Melkor, a.k.a. Morgoth (J. R. R. Tolkien, The Silmarillion)
- Mephiles the Dark (Sonic the Hedgehog series)
- Mephisto (Marvel Comics)
- Mephisto (Diablo series)
- Mephistopheles (Faust)
- Metroid Prime aka Dark Samus (Metroid Prime trilogy)
- Mephisto Pheles (Blue Exorcist)
- Mercutio (AdventureQuest Worlds online role-playing game)
- Milan Incubi (Strange)
- Mileena (Mortal Kombat)
- Mola Ram (Indiana Jones and the Temple of Doom movie)
- Mundus, Demon King (Devil May Cry)
Read more about this topic: List Of Fictional Demons