Taira no Masakado (平将門, died March 25, 940) was a Heian period provincial magnate (gōzoku) and samurai based in eastern Japan, notable for leading the first recorded uprising against the central government in Kyōto.

Yoshimochi[b] was one of the sons of Prince Takamochi, a grandson or great-grandson of Kanmu who was appointed the vice-governor of Kazusa Province (modern central Chiba Prefecture) in 889 (Kanpyō 1).

[16] At some point in his late teens, Masakado went to the capital city of Heian-kyō (Kyōto) and served in the household of the imperial regent Fujiwara no Tadahira.

He is said to have aspired for a position within the imperial police force, the Kebiishi, but failed to obtain court rank or any significant office in spite of his credentials and his patron's high status.

[19] On the other hand, the Konjaku Monogatarishū (c. 1120) gives another reason for the conflict, namely that Masakado's uncles had appropriated the lands the young man was supposed to inherit from his late father.

Masakado's uncle Taira no Kunika (平国香), who as Takamochi's eldest son was the head of the clan, might have tried to take over his younger brother Yoshimochi's property and place it under his control.

[10][15][19] In the 2nd month of 935 (Jōhei 5), Masakado and his men were ambushed by Mamoru's three sons, Tasuku, Takashi, and Shigeru, at a place called Nomoto (野本) in the district of Makabe (真壁郡), near the border between Hitachi and Shimōsa (modern Chikusei, Ibaraki), but managed to repel their attack; the three brothers all died in the battle.

On the 26th day of the 6th month of 936 (Jōhei 6), Yoshikane led his massive army to Hitachi, where he joined forces with Yoshimasa and Kunika's son Sadamori (who had been in the capital when his father was killed and initially took a neutral stance), whom he had prevailed upon to take part in the attack against Masakado.

They made contact at the border between Hitachi and Shimotsuke (modern Tochigi Prefecture) with Masakado, who went there to verify reports about a plan to launch a joint attack on him from the north.

Although he managed to surround his uncle in the governmental offices, Masakado, seemingly concerned about subsequent censure should he kill Yoshikane then and there, allowed him to escape through a gap in his western line.

(Shōmonki) Afterwards, Yoshikane burned a critical stable and some houses at Masakado's base in Toyoda District (豊田郡) in Shimōsa to weaken his ability to make war.

The fortunes of Edo and Tokyo seemed to wax and wane correspondingly with the respect paid to the shrine built to him at the kubizuka (ja); neglect would be followed by natural disasters and other misfortunes.