thumb|Portrait of Shimazu Tadayoshi
was a daimyō (feudal lord) of Satsuma Province during Japan's Sengoku period. He was born into the Mimasaka Shimazu family (伊作島津家), which was part of the Shimazu clan, but after his father Shimazu Yoshihisa died, his mother married Shimazu Unkyu of another branch family, the Soshū (相州家). Tadayoshi thus came to represent two families within the larger Shimazu clan.
Shimazu Katsuhisa, who presided over the Shimazu family, did not have a son and he was driven out by Shimazu Sanehisa, who was the head of yet another branch, the Sasshū (薩州家). Sanehisa then laid claim to be the head of the clan without being properly recognized by the rest of the families. Katsuhisa asked Tadayoshi for help to regain his position, and Tadayoshi sent his son Shimazu Takahisa to be adopted by Katsuhisa. In 1526, Katsuhisa handed over the position of the head of the family to Takahisa. In 1539 though, during the Battle of Ichiki Tsurumaru Castle, Tadayoshi defeated Katsuhisa (who would regain power later) and Takahisa came to be recognized by all members of the Shimazu clan as the head. He held a great amount of power, trading with the Ryūkyū Kingdom and Ming-dynasty China. He also arranged for massive purchases of arquebuses to make the clan prosperous for the planned unification of Kyūshū by Takahisa.
Tadayoshi wrote Iroha uta a set of 47 poems that conveyed Confucian moral principles in a comprehensible manner. Tadayoshi died in 1568 at the age of 77.