oni, in Japanese folklore, a type of demonic creature often of giant size, great strength, and fearful appearance. They are generally considered to be foreign in origin, perhaps introduced into Japan from China along with Buddhism. Cruel and malicious, they can, nevertheless, be converted to Buddhism. Though oni have been depicted in various ways in Japanese legend and art, sometimes also as women, they are characteristically thought of as pink, red, or blue-grey in colour, with horns, three toes, three fingers, and on occasion with three eyes.