Lifespan: Eishō 4 (1507) (?) to Tenbun 17 (1548) (?)
Rank: sengoku daimyō
Father: Iwamatsu Hisazumi (under an alternate theory, Iwamatsu Masazumi)
Children: Morizumi, Moriyoshi
Iwamatsu Ujizumi served as a sengoku daimyō of Kōzuke Province during the Sengoku period. Ujizumi was the fifteenth head of the Nitta-Iwamatsu clan.
The Nitta-Iwamatsu originated from the Iwamatsu township in the Nitta manor of Kōzuke in the early thirteenth century.
In the midst of long-standing differences between the Iwamatsu clan and their retainers, the Yokose clan, around 1507, Ujizumi was born as the son of Iwamatsu Hisazumi, a daimyō from the late Muromachi period. From 1529 to 1530, his older brother, Iwamatsu Masazumi, attempted to eliminate Yokose Yasushige, for his despotic behavior. Instead, Masazumi was attacked and took his own life. Partly carried by Yasushige, Ujizumi became the next head of the Iwamatsu family.
Thereafter, however, Ujizumi was unable to curtail the high-handedness exhibited by Yasushige, and, around 1548, took his own life. Ujizumi was succeeded by his son, Iwamatsu Morizumi, but, this allowed the Yokose clan to further increase their strength. In the era of Yasushige’s son, Yokose Narishige (later Yura Narishige), Nitta-Kanayama Castle was lost to the Yokose. Consequenntly, the Yokose usurped the Iwamatsu as the heads of the clan.
Owing to the age difference between Ujizumi and his older brother, Masazumi, there is a theory that Ujizumi was his son, but the facts are uncertain.