Lifespan: 2/7 of Eiroku 10 (1567) to 6/13 of Keichō 19 (1614)
Rank: bushō and daimyō
Title: Junior Fifth Rank (Lower); Governor of Nagato
Lord: Toyotomi Hideyoshi → Toyotomi Hideyori → Tokugawa Ieyasu → Tokugawa Hidetada
Han: Head of Hyūga-Takenabe
Father: Akizuki Tanezane
Mother: Daughter of Tawara Chikahiro
Siblings: Tanenaga, Takahashi Mototane, Taeshi, Ryūko (wife of Kii Tomofusa), sister (wife of Katō Masakata), sister (wife of Nagano Sukemori), sister (formal wife of Sagara Yorifusa), sister (wife of Itaba Nagatsune), sister (wife of Akizuki Naomasa)
Wife: [Formal] Daughter of 舜有
Children: Masachiyo (wife of Hino Tadaari), Ochō (wife of Akizuki Tanesada), Osai (wife of Hiramatsu Tokitsune), daughter (wife of Shimotsuma), Tatsuhime (wife of Kii Yoshitsuna and then Irie Chikashige), daughter (wife of Uchida Tanemasa)
Adopted Children: Tanesada, Taneharu
Akizuki Tanenaga served as a bushō and daimyō in the latter part of the Sengoku period and early Edo period. He was the first head of the Takanabe domain of Hyūga Province in Kyūshū.
Tanenaga was born in 1567 as the eldest son of Akizuki Tanezane, the sengoku daimyō of Chikuzen Province. In 1586, Tanenaga joined with his father to fight against Toyotomi Hideyoshi during the Kyūshū heitei, or Kyūshū Pacification, but lost and surrendered. Tanezane engaged in the rite of tonsure to demonstrate his sincerity, retiring to a secluded life, while Tanenaga succeeded him as head of the clan. Nevertheless, Hideyoshi ordered Tanenaga to move to Hyūga with a reduction in his domain to 30,000 koku.
Tanenaga deployed for the Bunroku-Keichō Expedition, a campaign launched by the Toyotomi administration on the Korean Peninsula during the last decade of the sixteenth century. In 1598, Tanenaga made contributions at the Siege of Ulsan Castle against the allied Chinese and Korean armies.
In 1600, Tanenaga defended Ōgaki Castle on behalf of the Western Army in the Battle of Sekigahara. However, soon after the Western Army suffered defeat in the main battle, Mizuno Katsunari convinced Tanenaga to switch allegiance to the Eastern Army. Tanenaga then joined with his younger brother, Takahashi Mototane, and Sagara Yorifusa, to kill Kumagai Naomori, Kakimi Kazunao, Kimura Yoshinobu, and his father, Kimura Toyotsune, in the castle, whereupon they surrendered. Thereafter, Fukuhara Nagataka, the commander in charge of defending the castle, opened the gates and surrendered to the Eastern Army. Tokugawa Ieyasu rewarded Tanenaga by recognizing his territory and enabling him to become the first head of the Takenabe domain of Hyūga in Kyūshū.
Tanenaga did not have a son so he adopted, as his son-in-law, Akizuki Tanesada, the son of Nagano Kaneyoshi. Tanesada, however, was deemed not suitable as a successor owing to his frail health. Instead, Akizuki Taneharu, the son of Tanesada and Tanenaga’s daughter (Ochō), was appointed as Tanenaga’s successor. This gave rise to discord among retainers who did not agree with this succession plan.
Tanenaga died in 1614 and Taneharu inherited the clan as planned.