Lifespan: Ōnin 2 (1468) to 11/8 of Daiei (1523)
Rank: bushō, sengoku daimyō
Title: Governor of Yamato
Father: Itō Sukekuni
Siblings: Tadasuke, Sukemune, Suketake, sister (wife of Sagara Nagatsune)
Wife: Daughter of the Aso clan, daughter of the Nakamura clan; [Consort] daughter of Fukunaga Sukiaki
Children: Daughter (wife of Fukunaga Genbei), son (mother from Nakamura clan), Sukemitsu, Yoshisuke, Gyokuren-fujin (wife of Shimazu Tadaharu), Sukeyoshi, daughter (wife of Sagara Nagamasa)
Itō Tadasuke served as a bushō and sengoku daimyō of Hyūga Province during the Sengoku period. Tadasuke was the eighth head of the Hyūga-Itō clan. He received one of the characters in his name from Ashikaga Yoshitada (later, Ashikaga Yoshitane), the tenth shōgun of the Muromachi bakufu.
In 1485, his father, Itō Sukekuni, died in battle against Shimazu Tadamasa so Tadasuke became the next head of the family. At the time of succession, Tadasuke was still in his youth so there were no notable actions, but, after growing up, he battled against the Shimazu to avenge the loss of his father as well as to expand his territory. Having observed these developments, the Ōtomo clan of Bungo Province sought to mediate a peace between the Itō and the Shimazu and, in 1495, Shimazu Tadamasa transferred 1,000 chō in Mimata-in in Hyūga to the Itō and the two sides reconciled. Later, in 1504, Tadasuke led forces to Miyakono Castle but, when confronted by Hongō Kazuhisa, withdrew his forces.
At one time, Tadasuke desired as a consort the attractive daughter of Fukunaga Sukeaki, the chief retainer. She was already wed to Tarumizu Mataroku, but Tadasuke forced them apart so she would become his consort by having Mataroku wed a daughter of the Kawasaki clan. In 1510, after this consort became pregnant, in the event a son was born, Tadasuke planned to remove from the line of succession a son earlier born with a daughter of the Nakamura clan. Nagakura Wakasa-no-kami Sukemasa (a chief retainer and the steward of Aya) and Tarumizu Tajima-no-kami criticized this plan, inviting the displeasure of Tadasuke. Sukemasa was then slandered by Inazu Echizen-no-kami Shigeyori who desired the role of steward of Aya. Fearing for their safety, on 9/1, Sukemasa and Tajima-no-kami holed-up in Aya Castle, triggering an event known as the Aya Revolt. On 10/17, the two of them committed seppuku, bringing the conflict to an end. At the height of these tensions, on 9/13, Itō Sukemitsu was born and designated as Tadasuke’s successor as the ninth head of the clan.
In the course of conflicts with the Shimazu and the Hongō clans, Tadasuke steadily gained control of the southern portion of Hyūga, succeeding in governing a majority of the territory. In 1522, he dispatched his younger brothers, Itō Sukemune and Itō Suketake to attack the base of the Hongō at Miyakono Castle. In 1523, he allied with the Kitahara clan to launch an assault on an auxiliary site of the Hongō at Nonomidani Castle. Although the castle was toppled, Tadasuke died at the encampment. He was fifty-six years old. His younger brother, Sukemune, suddenly died one month later on 12/10, so the Itō had to abandon the castle.
Tadasuke was succeeded by his son, Sukemitsu, but Sukemitsu was still in his youth so Sukemitsu’s maternal relatives led by Fukunaga Sukeaki monopolized power within the family.