Uesugi Masanori served as a bushō during the late-Muromachi period.  He was a retainer of Ashikaga Masatomo, the Horigoe kubō.

Masanori was born as the son of Uesugi Noritomo, serving as a secretary of the Kantō.  Masanori received one of the characters from the name of Ashikaga Yoshimasa, the eighth shōgun of the Muromachi bakufu and the character “nori” used for generations in the Uesugi clan, adopting the name of Masanori.

Masanori’s father, Noritomo, upon orders of Yoshimasa, was appointed as the secretary of the Kantō and together with Shibukawa Yoshikane, supported Ashikaga Masatomo, the Horigoe kubō.  In 1461, owing to slander by Yoshikane, Masatomo believed the Ōgigayatsu-Uesugi family planned to rebel and suspected Noritomo so Noritomo took his own life.  Anxious about the situation, Yoshimasa approved the removal of Yoshikane and succession by Masanori to the position as the secretary of the Kantō, ordering Masanori to serve Masatomo in Izu Province.

In 1462, Masanori impeached Yoshikane and after Yoshikane refused, Masanori joined with Uesugi Fusaaki, the deputy shōgun of the Kantō, and plotted the removal of Ashikaga Shigeuji, the Koga kubō.  In 1465, Masanori, with the support of a relative, Oshika Norimitsu (a member of the Suruga-Imagawa clan) deployed to the Kantō and, together with Fusaaki and Ōta Dōkan of the Ōgigayatsu-Uesugi, fought against supporters of Shigeuji at the Ōta manor in Musashi Province but Fusaaki suddenly died the following year so the forces withdrew.

In 1476, after the death of Imagawa Yoshitada, the military governor of Suruga, owing to the young age of Yoshitada’s lineal heir, Tatsuōmaru (later known as Imagawa Ujichika), Oshika Norimitsu surfaced as a successor to the clan.  Masanori then joined Ōta Dōkan and deployed with a faction supporting Norimitsu as the next head.  This faction was opposed by Tatsuōmaru’s uncle, Ise Moritoki (later known as Hōjō Sōun), after which a settlement was reached by which Norimitsu would serve as a proxy head of the clan until Tatsuōmaru became an adult.  Following this settlement, Masanori withdrew.

Thereafter, when an opportunity arose for peace between the Uesugi clan and the Koga kubō, Masanori appealed to Masatomo in regard to the difficulty of continuing the battle and encouraged him to pursue a settlement.  He then engaged in negotiations to coordinate with the bakufu.  As a result, the governance of the Horigoe kubō was limited to Izu Province, an outcome for which Masatomo deeply resented Masanori.  Moreover, when Masatomo attempted to remove his son, Ashikaga Chachamaru, from the line of succession, he became enraged when Masanori strongly admonished him.  Masanori was then ordered to take his own life whereupon he committed seppuku.

The year in which Masanori took his own life is not certain.  Nevertheless, his death is surmised to be related in time to the circumstances whereby Ōta Dōkan was murdered by his lord, Uesugi Sadamasa, in the seventh month of 1486 and Oshika Norimitsu was decimated by Ise Moritoki in the eleventh month of 1487.