Candaulism is most commonly defined as a sexual practice, or the fantasy of the practice, where a man exposes his female partner, or intimate images of her, to others for their voyeuristic pleasure. It is sometimes defined as the practice of two people having sexual intercourse while a third partner watches. The voyeur usually observes from a hidden location.
The term comes from the activities of King Candaules; he was an ancient monarch who planned to show his naked wife to his servant without her knowledge. It was coined by German psychiatrist Richard von Krafft-Ebing in his famous book Psychopathia Sexualis.