Shimazu Tadayoshi (Soshu)
- Born: 1492
- Died: 1568
- Titles: Sagami no kami
- Sons: Shimazu Takahisa, Kiire Hisamichi
- Other Names: 日新斎 (Jisshinsai)
- Japanese: 島津忠良 (Shimazu Tadayoshi)
After his father Isaku Yoshihisa died when Tadayoshi was three years old, Tadayoshi was raised by his mother Shimazu Tokiwa, and his grandfather Shimazu Hisayasu. Hisayasu died in battle in 1500, when young Tadayoshi was age eight. Tadayoshi's mother Tokiwa then married Shimazu Yukihisa, head of the Sôshû Shimazu, making Tadayoshi heir to both the Isaku and Sôshû Shimazu lines.
In 1526 or 1527, at the request of Shimazu Katsuhisa, Tadayoshi's son Torajumaru (Shimazu Takahisa) was adopted by Katsuhisa as heir to the main Shimazu lineage. This adoption & amendment to the line of succession was opposed, however, by Shimazu Sanehisa of the Sasshû line, leading to numerous battles between Tadayoshi, Takahisa, and their karô Ijûin Tadaaki on one side, and Sanehisa on the other. Sanehisa was eventually defeated, in 1539, at Kaseda, Kawanabe, Ichiki, and Murasakibaru, and the Sasshû family were driven out of Kagoshima. Tadayoshi then made Kaseda castle his seat.
Tadayoshi meanwhile took the tonsure in 1527, taking on the monastic name Jisshinsai, and studied Zen, waka poetry, and Confucianism, under Shunden and Shun'yû, students of Keian Genju. In 1545-1546, he wrote a new version of the classic iroha poem which earned great praise from the cultural elite of Kyoto after Tadayoshi shared the poem with Konoe Taneie. The poem went on to play a significant role in Edo period samurai education within Satsuma domain.
His son Takahisa went on to become head of the main Shimazu house, while his daughter O-Minami married Kimotsuki Kanetsugu.
Tadayoshi died at Kaseda in 1568, at the age of 77.
- "Shimazu Tadayoshi," Satsuma Shimazu-ke no rekishi, Shôkoshûseikan official website.