An Oni mask is a traditional Japanese mask representing a demon or ogre from Japanese folklore. Oni are typically depicted with fierce expressions, sharp teeth, and horns, symbolizing malevolent spirits or gods of mischief and retribution. These masks are used in various cultural and theatrical performances, such as Noh and Kabuki theatre, and during festivals to ward off evil spirits and bring good fortune. The striking design and powerful symbolism make Oni masks a distinctive and important element of Japanese culture.