Demons are a type of species in the Mortal Kombat universe.
Quan Chi, Ashrah, Sareena, Kia, Jataaka, Siann, Mika and Sora are known demons. They can hide their appearance underneath a human façade, but otherwise seem to be the same as Oni. Quan Chi was originally an Oni, until he became a demon with his mastery over sorcery and magic. Siann, Mika, and Sora were originally lifeless corpses until Quan Chi saved them. Other generic demons have appeared in Mortal Kombat: Shaolin Monks as regular minions that players fight later in the game.
Different classes included the Demon Wards, Demon Warmonger and small Imps. Other classes of demons that wore armor and carried weapons are Demon Archers, Demon Captains, Demon Generals and Demon Handlers.
- There was going to be another class of the Netherrealm's high level demons called the Elder Demons, including the character Baphomet, mentioned in the Krypt and Kontent gallery of Mortal Kombat: Deadly Alliance. These dark creatures are similar to the Elder Gods, only less powerful.
- As explained in their endings in MK2011 and Armageddon endings respectively, Smoke and Hsu Hao may in actuality be some manner of demons themselves, with Smoke's variation being known as an Enenra.