An incubus is a male demon of European folklore and demonology believed to visit women at night and lie upon them as they sleep. Its female counterpart is the succubus. The idea has roots in ancient Near Eastern and classical beliefs, was systematized by medieval theologians, and is now widely explained by researchers as an interpretation of sleep paralysis and nightmares.
Incubus at a glance
| Type | Male night demon of folklore and demonology |
|---|---|
| Etymology | Latin incubare, "to lie upon" |
| Female counterpart | Succubus |
| Ancient parallels | Mesopotamian lilu spirits; Roman fauns and silvani |
| Key texts | Augustine, City of God; Malleus Maleficarum (1486); Sinistrari, De Daemonialitate |
| Modern explanation | Sleep paralysis and hypnagogic hallucinations |
Name and early origins
The word incubus comes from the Late Latin incubus, "nightmare," from incubare, "to lie upon." It captures the central feature of the belief: a being that presses down upon a sleeper. Similar figures appear in many cultures. Mesopotamian texts mention the lilu, a class of spirits thought to disturb women in their sleep, and Roman writers told of woodland beings such as fauns and silvani who approached sleepers at night.
The idea of a crushing night visitor is also preserved in the English word "nightmare," whose second element comes from the Old English mare, a spirit believed to sit on the chest of sleepers. The German Alp, the Scandinavian mare and many other folk figures share this core image.
The incubus in Christian demonology
Christian authors discussed incubi from late antiquity onward. Augustine of Hippo, in The City of God, noted widespread reports that beings the people called incubi had approached women, and he declined to dismiss them outright. Medieval scholastic theologians, including Thomas Aquinas, debated how spirits without bodies could have physical relations with humans. One influential answer held that a demon could take on an assumed body and transfer human seed collected in the form of a succubus, so that any child would have a human father.
Legends of children born from such unions circulated widely. Geoffrey of Monmouth's twelfth-century account of Merlin claimed that the wizard was fathered by an incubus. The offspring of such a union was sometimes called a cambion.
Witch trials and the Malleus Maleficarum
In the era of the European witch hunts, the incubus became part of accusations of witchcraft. The Malleus Maleficarum (1486), the witch-hunting treatise by the Dominican Heinrich Kramer, argued that witches willingly entered into relations with incubi as part of their pact with the Devil. It listed remedies against unwanted visitations, including confession, the sign of the cross, exorcism, moving to another place and excommunication of the demon. Such ideas fed into the questioning of accused people during trials, alongside notions such as the Devil's mark.
In the seventeenth century the Franciscan Ludovico Maria Sinistrari wrote De Daemonialitate, which proposed that incubi were not devils but rational creatures with bodies of their own, somewhat like the elementals of Renaissance philosophy. The book was not published until the nineteenth century.
The scientific view
Modern researchers commonly connect incubus experiences with sleep paralysis, a state in which a person wakes while the muscle paralysis of REM sleep persists. People in this state may feel pressure on the chest, difficulty breathing, and the vivid sense of a presence in the room, sometimes with frightening visual or tactile hallucinations. Surveys suggest that a substantial minority of people experience at least one episode in their lives. Across cultures these experiences have been interpreted through local figures, such as the "night hag" of English and Newfoundland folklore. This explanation accounts for the classic features of incubus reports without requiring any supernatural being, and there is no scientific evidence that such entities exist.
Parallels around the world
Beliefs in nocturnal visitors who press on or seduce sleepers are found far beyond Europe. Folklorists have compared the incubus with the Turkish karabasan, the Southern African tokoloshe, and the boto, a river dolphin of Amazonian folklore said to take human form and seduce women. Newfoundland tradition speaks of being "hagged" by the Old Hag. These figures differ greatly in their cultural meanings: some are feared as predators, others are used to explain unexpected pregnancies or illness, and others belong to a broader world of tricksters and nature spirits.
Scholars of folklore such as David Hufford have argued that the remarkable similarity of these accounts across unconnected cultures points to a shared human experience, which each society interprets in its own terms. In Jewish tradition, related roles were given to night demons associated with Lilith, and some writers linked the incubus to fallen angels or to demons such as Belial.
In art and later culture
The incubus inspired one of the best-known images of the Romantic era, Henry Fuseli's painting The Nightmare (1781), which shows a demon squatting on the chest of a sleeping woman. The figure has since appeared in Gothic fiction, horror films and music. In some modern occult and Christian deliverance writings, incubi are still discussed as spiritual threats, and people troubled by such experiences often seek comfort in prayer or in practices of psychic protection. Medical advice is appropriate for frequent episodes of sleep paralysis, which are often linked to disrupted sleep.
Related entries
On The Mystica today: Psychic protection · Dream dictionary
Frequently asked questions
What is the difference between an incubus and a succubus?
In European folklore the incubus is a male demon believed to visit women at night, while the succubus is its female counterpart said to visit men. Medieval theologians sometimes argued that the same demon could act in both forms, collecting seed as a succubus and then transferring it as an incubus.
What causes the feeling of an incubus at night?
Researchers link these experiences to sleep paralysis, when the mind wakes before the body's REM-sleep paralysis ends. People may feel chest pressure, breathlessness and a menacing presence, sometimes with vivid hallucinations. Stress, irregular sleep and sleep deprivation make episodes more likely, and a doctor can advise if they happen often.
Where does the word incubus come from?
The word comes from Late Latin incubus, meaning nightmare, derived from the verb incubare, to lie upon. The name describes the belief that the demon lay on top of sleepers. The related word succubus comes from succubare, to lie beneath, and English nightmare preserves the older idea of a mare that sat on sleepers.
Sources and further reading
This entry replaces an article from the original Mystica encyclopedia (online since 2001). It was rewritten from the sources above by The Mystica Editorial Team under our editorial standards. Last reviewed: September 30, 2026.