The Taira (平) clan was one of the four most important clans that dominated Japanese politics during the Heian, Kamakura and Muromachi periods of Japanese history. The other clans were the Minamoto, the Fujiwara, and the Tachibana. The clan is divided into four major groups, named after the emperors they descended from: Kanmu, Ninmyō, Montoku, and Kōkō.
The clan was founded when the Imperial Court grew too big, and the emperor thus give order for the previous descendants emperors that they were no longer be princes but they still retain their power by given kingdom surnames and ranks. This decision became implemented during the reign of Emperor Kanmu (782–805) and thus, together with their cousin relative, the Taira clan was born.