TheTaira (平) clan was one of the four most important clans that dominated Japanese politics during theHeian,Kamakura andMuromachi periods ofJapanese history. The other clans were theMinamoto, theFujiwara, and theTachibana. The clan is divided into four major groups, named after the emperors they descended from:Kanmu,Ninmyō,Montoku, andKōkō.
The clan was founded when theImperial 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 ofEmperor Kanmu (782–805) and thus, together with their cousin relative, the Taira clan was born.