- Birth: 1502
- Death: 1550
- Other name: Ôtomo Yoshinori
- Distinction: Lord of Bungo
- Sons: Otomo Yoshishige, Shioichimaru (d. 1550), (Ôuchi) Yoshinaga, Otomo Chikasada
- Japanese: 大友 義鑑 (Ootomo Yoshiaki)
Yoshiaki was a son of Ôtomo Yoshinaga and was married to a daughter of Ôuchi Yoshioki. He worked to secure Ôtomo influence over Bungo and clashed with the Ôuchi and Shôni. He inherited a troubled retainer band and had to contend with his independent-minded brother, Yoshitake. He indicated that he wished to name a younger son as his heir. This prompted a group of retainers who supported his eldest son, Yoshishige, to conspire against him. In February of 1550 those retainers, led by Irida Chikazane, attacked Yoshiaki's residence, mortally wounding Yoshiaki and killing his son, Shioichimaru and Shioichimaru's mother.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005