The Akechi clan (明智氏 Akechi-shi) was a branch of the Toki clan, descended in turn from the Seiwa Genji. The Akechi clan prospered towards the latter part of the Sengoku period.
The Akechi became independent after the Toki were usurped by the Saitō clan around 1540. They refused to submit to Saitō Yoshitatsu who attacked their castle at Nagayama.
Akechi Mitsuhide later served the Shōgun Ashikaga Yoshiteru and Ashikaga Yoshiaki. After mediating a meeting between Yoshiaki and Oda Nobunaga, Mitsuhide became a powerful general servant of the Oda clan.
However, after 1582, Mitsuhide trapped Nobunaga at Honnō-ji and forced him to commit suicide.
The collapse of the Oda gave the Akechi the power of the Shogunate, but it lasted only for a few days: Akechi Mitsuhide was killed at the Battle of Yamazaki along with most of the clan's servants twelve days after the Honnō-ji incident, and the clan ceased to exist.