In medieval legend, an incubus (plural incubi; from Latin incubare, "to lie upon") is a demon in male form supposed to lie upon sleepers, especially on women in order to have sexual intercourse with them. There several possible explanations for the incubus legends:
- They form part of the well-attested Medieval preoccupation with sin, especially sexual sins of women.
- Actual rapes of sleeping women were attributed to demons by rapists in order to escape punishment.
- The feeling of smothering while sleeping is known to physicians. The modern term for this common disorder is sleep hypnosis or sleep paralysis.
See also: succubus.