Onmyo-Za (also Onmyouza or Onmyoza; Japanese: 陰陽座, literally "Onmyou gathering") are a Japanese heavy metal band who released their first commercial album in 1999. They play quite orthodox heavy metal music comparable to Iron Maiden or Judas Priest, mixed with elements from Japanese folk and pop music. Since their debut, they have appeared in traditional clothing characteristic of Japan's Heian period. Their name refers to the gathering of yin and yang, and the theme of opposites and cosmic dual forces are prevalent in their lyrics.