A cacodemon (or cacodaemon) is an evil spirit or (in the modern sense of the word) a demon.

The opposite of a cacodemon is an agathodaemon or eudaemon, a good spirit or angel.

In psychology, cacodemonia (or cacodemonomania) is a form of insanity in which the patient believes that they are possessed by an evil spirit.

In astrology, the 12th house was once called the Cacodemon for its association with evil.

[2][3] Defined as "a noise-making devil", Jane Davidson has noted an illustrated example of a cacodemon in editions of Ulisse Aldrovandi's Monstrum Historia (Story of Monsters) as late as 1696.