Tomoe Gozen was a female samurai during the Genpei War of 1180–1185 CE. Though female warriors were not uncommon in Japan at the time, Tomoe Gozen is one of very few female samurai, highly trained and skilled in horseback riding, archery, and sword fighting. She was a senior captain under general Minamoto no Yoshinaka, and either his attendant or consort as well, depending on the source. Tomoe Gozen's surname is not known, as Gozen is simply a title, somewhat like "Lady."

The earliest written source regarding Tomoe Gozen is from the 14th century Japanese classic, The Tale of the Heike, which in turn is derived from oral tradition. This source describes Tomoe Gozen as almost supernaturally strong, very beautiful, and surpassing her male colleagues in skill and bravery.

On 21 February 1184, Yoshinaka and Tomoe Gozen fought a decisive battle against Yoshinaka's cousin, Minamoto no Yoritomo. Yoshinaka's forces were outnumbered and Yoshinaka, knowing they had lost the battle, urged Tomoe Gozen to flee. The Tale of the Heike tells that she obeyed him, but after capturing a head from the enemy.

Other sources on Tomoe Gozen vary widely in their description of her actions during this final battle. Some say that it was Yoshinaka's head she ran away with, to prevent it from falling into the hands of the enemy. Others tell that she refused to leave Yoshinaka, fighting at his side until both died. Those that say she escaped with her life also have alternate endings; Tomoe Gozen either committed suicide or became a nun after Yoshinaka's death.

The mystery and legend surrounding Tomoe Gozen's life, along with her extraordinary skill, valor, and beauty, have led some to believe that she was the reincarnation of an ancient Japanese river goddess. In any case, she has remained a favorite in Japanese literature and lore to the present day. Versions of Tomoe Gozen can be seen in manga, anime, and drama in Japan, as well as in a trilogy of fantasy novels by American author Jessica Amanda Salmonson.