Hōjō Masako (北条 政子, 1157 – August 16, 1225) was a Japanese politician who exercised significant power in the early years of the Kamakura period, which was reflected by her contemporary sobriquet of the "nun shogun".

[1] She was instructed in horseback riding, hunting, fishing, and she ate with men rather than with the women of the household.

As Yoritomo's wife, she participated in government administration and eventually became a representation of power for the Hōjō clan.

[4] The same year a disillusioned Imperial Prince Mochihito, son of Emperor Go-Shirakawa, called on members of the Minamoto still remaining in Japan to overthrow the Taira.

The Minamoto center of power was the city of Kamakura, to the east of Izu in Sagami Province.

In 1180, Masako's elder brother Munetoki was killed at Battle of Ishibashiyama and Yoshitoki became heir of Hōjō clan.

In 1183, Yoritomo's rival and cousin Minamoto no Yoshinaka took Kyoto, forcing the Taira (and Emperor Antoku) to Shikoku.

[citation needed] Yoritomo was now the undisputed leader of Japan and his wife Hōjō Masako and her family had stood by her husband through it all.

Yoritomo's allegiance to his wife's family and her dislike of her brothers-in-law, as well as an internal power struggle brought on by the three brothers, eventually resulted in the arrest and execution of Yoshitsune and Noriyori.

[citation needed] Yoritomo bestowed the titles of shugo and jitō on loyal followers to undermine Emperor Go-Shirakawa's authority and the central government's control in the provinces while Kyoto was relegated to a ceremonial role and power shifted to center around Kamakura.

Since her husband was dead, she shaved her head and became a Buddhist nun, receiving a tonsure from the priest Gyōyū.

Along with her father Tokimasa and her brother Yoshitoki, Masako created a council of regents for the eighteen-year-old Yoriie.

Hōjō Tokimasa abdicated in 1205, and was sent off to a monastery in Kamakura, where he shaved his head and became a monk, dying in 1215.

In 1219, Sanetomo was killed by his nephew Kugyō, son of his murdered elder brother Yoriie.

[6] Azuma Kagami, the official chronicle of the Kamakura shogunate, tells that Masako summoned the vassals and had these words delivered to them by Adachi Kagemori, the Vice-Governor of Akita Fortress:[7] Regent Yoshitoki and his eldest son, Hōjō Yasutoki, responded to the rebellion by regaining Kyoto,resulting in the exile of Go-Toba.

Masako continued to consolidate rule under the advisory council, manage relationships and connections between imperial and aristocratic families, and administer judgments and postwar rewards.