Taira no Masakado (平 将門?, died March 25, 940) was a samurai in the Heian period of Japan, who led one of the largest insurgent forces in the period against the central government of Kyoto.
Masakado was a member of the Kammu Taira clan of Japan. He was the son of Taira no Yoshimochi, Chinjufu Shogun. His childhood name was Sōma Kojirō. Taira no Masakado was a powerful landowner in the Kantō region. He is regarded as the first bushi because he was the first to lead a self-governing party.
His life is detailed in the Shōmonki, a detailed book about his life believed to have been completed as early as the 940s by an anonymous author. Due to the religious and political nature of the account, it was most probably written by a monk or aristocrat closely connected to Masakado himself.
In 939 (Tengyō 2, 12th month) during the Heian period of Japanese history, Masakado led a minor rebellion which is also known as Jōhei Tengyo no ran. The armed struggle began when Masakado led an attack on an outpost of the central government in Hitachi Province, capturing the governor. In December of that year, he conquered Shimotsuke and Kōzuke Provinces; and he claimed the title of Shinnō (New Emperor).
Masakado killed his uncle Kunika who was part Taira. The central government in Kyoto responded by putting a bounty on his head, and fifty-nine days later his cousin Sadamori, whose father Masakado had attacked and killed, and Fujiwara no Hidesato, killed him at the Battle of Kojima (Shimōsa Province) in 940 and took his head to the capital.