Hojo Masako (1157-1225) was the wife of Minamoto no Yoritomo, founder and first shogun of the Kamakura shogunate of Japanese history. Her sons Minamoto no Yoriie and Minamoto no Sanetomo were the second and third shoguns, respectively, of the Kamakura shogunate.

After Yoritomo's death in 1199, Masako became a Buddhist Nun and along with her father Hojo Tokimasa and brother Hojo Yoshitoki , usurped all political and military power of the shogunate, relegating the position and title of Seii Taishogun, or shogun, to a mere figurehead.

After the murder of the shogun Sanetomo in 1219, Masako and Yoshitoki suppressed the Jokyu Incident of 1221 and installed Kujo Yoritsune as a the fourth shogun in 1226. Controlling the puppet shogun and overall shogunate until her death, Masako became to be called the Ama Shogun or "Nun Shogun".

See also: Hojo clan.