Lifespan: Daiei 4 (1524) to 3/22 of Tenbun 17 (1548)
Title: Vice Minister of the Sovereign’s Household, Governor of Buzen
Father: Ryūzōji Tanehisa
Siblings: Tanemitsu, Ienari, Taneaki
Wife: Daughter of Ryūzōji Iekado
Ryūzōji Tanemitsu served as a bushō during the Sengoku period. He was the eighteenth head of the Ryūzōji clan of Hizen Province.
Tanemitsu was born as the son of Ryūzōji Tanehisa, the seventeenth head of the Ryūzōji clan, kokujin, or provincial landowners, in Hizen. Similar to his father, Tanemitsu received support from Ryūzōji Iekane of the Mizugae-Ryūzōji but was serving in the capacity akin to a puppet and, as a result, came into conflict with Iekane. For a period of time, he went into exile and sought refuge with the Ōuchi clan. In 1545, many members of the Ryūzōji were slaughtered in a plot led by Baba Yorichika. In 1546, Tanemitsu cooperated with Iekane to seek retribution and kill Yorichika.
In 1547, Tanemitsu was appointed by Ōuchi Yoshitaka to serve as the local governor of Hizen but, in 1548, died of illness. He did not have an heir so, following consultations among family members, Ryūzōji Tanenobu (later known as Ryūzōji Takanobu), the great-grandson of Iekane from the Mizugae-Ryūzōji cadet family inherited the headship of the main branch of the Ryūzōji clan. Numerous retainers, however, were dissatisfied with the succession by Tanenobu and, in 1551, an internal conflict erupted when former retainers including Tsuchibashi Hidemasu backed Ryūzōji Akikane as the successor.
Tanemitsu’s widow (the daughter of Ryūzōji Iekado) remarried to Takanobu. His daughter named Oan wed Oda Shigemitsu, the lineal heir of Oda Masamitsu. After Shigemitsu was murdered for betraying Takanobu, she remarried a daimyō named Hata Chikashi.