The Ōtomo clan (jap. 大友氏, Ōtomo-shi) was a Japanese clan traced back to Fujiwara no Nagaie (1005-1064).
The clan played an important role in Kyūshū, the southernmost of Japan's four main islands, from the Kamakura period to the Sengoku period.
As one of the three major clans of Kyūshū, the Ōtomo, along with the Shōni and the Shimazu, had to make the greatest sacrifices in defense against the Mongol invasions of Japan in 1274 and 1281.
They also played an important role in the establishment of the Ashikaga Shōgunate in 1336. Bushi of the Ōtomo clan fought side by side with Ashikaga Takauji and enabled him to win some decisive battles, for example the Battle of Sanoyama, which in turn secured the clan influential positions in the new shogunate.