In Japanese folklore, an oni is a horned ogre-like yōkai commonly shown with an iron club.
Oni are typically depicted as large, powerful beings with horns, fangs, wild hair, and brightly colored skin. Their most recognizable weapon is the kanabō, a heavy club often rendered with metal studs. Stories may portray oni as violent monsters, punishers, guardians, or inhabitants of Buddhist hells.
The annual Setsubun custom of throwing roasted soybeans while saying “Oni wa soto, fuku wa uchi” symbolically drives oni out and invites good fortune in. This practice helped make the image familiar well beyond religious texts.
Oni are not identical to Western devils or demons. Their meanings vary by story and period, and some Japanese Buddhist paintings show them serving as guardians. They are also different from tengu, who are associated with mountains and birdlike or long-nosed features.