Akamatsu Mitsusuke (1381–1441) was a prominent Japanese daimyo (feudal lord) of the Muromachi period and the head of the Akamatsu clan. He is primarily recognized for his role in the assassination of the sixth Ashikaga shogun, Ashikaga Yoshinori, an event historically known as the Kakitsu Incident.
The Akamatsu clan held significant administrative and military power as shugo (provincial governors) over the provinces of Harima, Bizen, and Mimasaka. Mitsusuke assumed leadership of the clan following the death of his father, Akamatsu Yoshinori. His tenure coincided with the shogunate of Ashikaga Yoshinori, who was known for his efforts to centralize authority and reduce the power of regional daimyo through confiscation of lands and interference in clan successions.
The tension between the shogunate and the Akamatsu clan escalated when Mitsusuke suspected that the Shogun intended to seize his domains and grant them to a rival branch of the Akamatsu family. In response to this perceived threat, Mitsusuke invited Shogun Yoshinori to a banquet at his residence in Kyoto on July 12, 1441. During the event, Mitsusuke’s retainers assassinated the Shogun.
Immediately following the assassination, Mitsusuke and his supporters fled Kyoto and returned to their stronghold in Harima Province. The shogunate’s administration, though thrown into temporary disarray, organized a punitive expedition led by the Yamana clan. Mitsusuke’s forces were unable to withstand the assault; he committed ritual suicide in September 1441 as his castle fell. The aftermath of the Kakitsu Incident resulted in the temporary dissolution of the Akamatsu clan's power and is cited by historians as a significant moment in the decline of the Ashikaga shogunate’s central authority.