Ashikaga Ujimitsu (足利氏満?) (1359–1398) was a Nanboku-chō period warrior and the Kamakura-fu's second Kantō kubō, or Shogun Deputy. Son of first Kantō Kubō Ashikaga Motouji, he succeeded his father in 1367 at the age of nine when this last suddenly died during an epidemic. It was during his reign that the Kanto Kubō title became common enough to appear for the first time in writing. It is in fact contained in a 1382 entry of the Tsurugaoka Jishoan (鶴岡事書安?). This title was in itself rebellious, because it was first adopted by Takauji himself and its use therefore implied equality with the shogun. In fact, sometimes the Kanto Kubō was called Kantō Shogun.
He was the first Kantō Kubō to openly aspire to the shogunate, and his relationship with shogun Ashikaga Yoshimitsu in Kyoto consequently deteriorated to the point of being likened to that of "cats and dogs".
Ujimitsu became Kantō Kubō at the age of nine when his father suddenly died at the age of 29 during an epidemic. Because of his extremely young age, he was given Uesugi Noriaki as a regent and Rinzai Zen priest Gidō Shūshin as a tutor. (Noriaki however died the following year and was replaced by his son Yoshinori.) Immediately after Ujimitsu's accession to power, Uesugi Noriaki left Kamakura for Kyoto to represent the Kantō Kubō at Ashikaga Yoshimitsu's accession ceremony. Taking advantage of his absence, some Musashi families, led by the Kawagoe and the Takasaka clans, revolted against Ashikaga rule in the so-called Hei Revolt (平一揆 Hei Ikki?), and were soon joined by Shimotsuke Province's Utsunomiya clan. The Uesugi however remained faithful and defeated the coalition.