- Birth: 1477
- Death: 1528/12/20
- Titles: Sakyô-daibu, kanrei (1508-1518)
- Distinction: Lord of Suo, Nagato, and Iwami
- Sons: Ôuchi Yoshitaka, Hirooki
Yoshioki was the eldest son of Ôuchi Masahiro and ruled from Yamaguchi in Suo Province. He worked to increase the power of the Ôuchi and came into conflict with the Ôtomo of Bungo (Kyushu) and the rising Amako of Izumo. In 1508 Yoshioki took up the cause of the deposed shôgun, Ashikaga Yoshitane, and marched on Kyoto, for which he was named kanrei. In 1511 he marched with Hosokawa Takakuni to defeat Hosokawa Masataka and Hosokawa Sumimoto at Funaokayama north of Kyoto. With the assistance of the Rokkaku he returned some semblance of order to the capital, but was forced to return to Yamaguchi in 1518, both to thwart the ambitions of the Amako and to avoid an embarrassing financial scandal brought about by his own generosity. He clashed with Amako Tsunehisa, and the two became known as great rivals, fighting campaigns in Aki and Iwami Provinces. Yoshioki married a daughter to Ôtomo Yoshiaki, and she would produce a future head of the Ôuchi, Yoshinaga. He died of illness 1528/12/20.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005