Lifespan: 1/15 of Tenbun 10 (1541) to 1/21 of Tenshō 11 (1583)
Rank: Koga kubō
Title: Junior Fifth Rank (Lower), Chief of the Imperial Cavalry of the Left Division, Junior Fourth Rank (Lower), Assistant Captain of Imperial Guards of the Right Division
Clan: Ashikaga – branch in the Kantō Region
Bakufu: Fifth Koga kubō of the Muromachi bakufu
Father: Ashikaga Haruuji
Mother: Hōshun-in (daughter of Hōjō Ujitsuna)
Siblings: Fujiuji, Yoshiuji, Fujimasa, Teruuji, Iekuni
Wife: [Formal] Jōkōin (daughter of Hōjō Ujiyasu)
Children: Ujihime, Umechiyo-ōmaru, Daughter
Ashikaga Yoshiuji served as the fifth Koga kubō from 1552 to 1583 during the Sengoku period. Yoshiuji was the son of Ashikaga Haruuji, the fourth Koga kubō. His mother was Hōshunin, the daughter of Hōjō Ujitsuna. His formal wife was Jōkōin, the daughter of Hōjō Ujiyasu. Ashikaga Fujiuji and Ashikaga Fujimasa were half-brothers of a different mother.
Yoshiuji was born at Odawara Castle on 1/15 of 1541 as the second son of Haruuji. In his youth, he was called Umechiyo-ōmaru. After Haruuji lost to the rival Hōjō in the Battle of Kawagoe Castle, Haruuji was taken away and incarcerated at Kurihashi Castle, whereupon the Hōjō insisted that Yoshiuji become his successor as the Koga kubō. In the eleventh month of 1554, Yoshiuji’s coming-of-age ceremony was held at Kasai Castle controlled by the Hōjō rather than at Koga Castle, which served as the palace seat for the Koga kubō. It was at this time that Yoshiuji was given his name with one of the characters from the name of Ashikaga Yoshifuji, the shōgun of the Muromachi bakufu, while Hōjō Ujiyasu, his uncle, presided over the ceremony. In the spring of 1558, Yoshiuji departed from Kasai Castle to pay a visit in his capacity as the Koga kubō to the sacred Tsurugaoka-Hachiman Shrine in Kamakura. After returning to his territory in late summer, he relocated to Sekiyado Castle instead of the traditional palace seat of the Koga kubō at Koga Castle. This was done for political purposes at the direction of the Hōjō.
Meanwhile, after Uesugi Kenshin became the deputy of Kantō, he determined that Ashikaga Fujiuji, the eldest son of Haruuji, should become the Koga kubō. Kenshin refused to recognize the succession of Yoshiuji as the Koga kubō on the grounds that he was the second son of Haruuji and born to a different mother than Fujiuji.
Caught in the middle of the ongoing battle between the Hōjō of Kantō and opposition forces led by the Uesugi clan, Yoshiuji moved in-between locations such as Odawara to keep his distance from the epicenter of Koga.
Around 1570, Kenshin entered into an alliance with Hōjō Ujimasa of Sagami Province. As a condition of this settlement, Kenshin agreed to recognize the propriety of Yoshiuji as the successor to Haruuji. This enabled Yoshiuji to finally return to his position as the Koga kubō in Koga. As a further condition, Hōjō Ujiteru, the son of Ujiyasu, would serve as his guardian, making Yoshiuji a puppet of the Hōjō. Yoshiuji likely wed Jōkōin at this time.
Yoshiuji died early in 1583. His eldest son, Umechiyo-ōmaru met a premature death. The retainers of the Koga kubō backed Ashikaga Ujihime, the older sister of Umechiyo-ōmaru, to serve as the lord of Koga Castle.
Owing to regret at the end of the Ashikaga blood line, Toyotomi Hideyoshi arranged for the marriage of Ujihime to Ashikaga Kunitomo, the grandchild of Ashikaga Yoshiaki, who was the Oyumi kubō. This gave rise to the Kitsuregawa clan, descendants of the Ashikaga.