Lifespan: Bunmei 11 (1479) to 1/23 of Tenbun 14 (1545)
Title: Governor of Bungo
Lord: Shōni Sukemoto, Shōni Fuyuhisa
Father: Ryūzōji Iekane
Siblings: Iesumi, Iekado, Gōkaku, sister (wife of Oho Tanemune)
Children: Kaneie, Sumiie, Yorisumi, Kakei, daughter (formal wife of Chiba Tanetsura), daughter (wife of Baba Masakazu), daughter (wife of Inuzuka Naoie)
Ryūzōji Iesumi served as a bushō during the Sengoku period. Iesumi was the uncle of Ryūzōji Takanobu and Nabeshima Naoshige.
In 1479, Iesumi was born as the lineal heir of Ryūzōji Iekane.
Initially, Iesumi, together with Iekane, served as retainers of the Shōni clan. In 1530, at the Battle of Tadenawate, he fought valiantly for the Shōni clan, contributing to the defeat of the Ōuchi clan. After his father was alienated from Shōni Fuyuhisa, Iesumi joined him in defecting from the Shōni. Later, following a reconciliation, Iesumi and his father returned to the service of the Shōni.
Iesumi endeavored to strengthen the position of the Ryūzōji family by facilitating marital relations with the Nabeshima clan (retainers) and their former lords, the Kyūshū-Chiba clan. Iesumi adopted his younger brother, Ryūzōji Iekado, and had him succeed to the Mizugae-Ryūzōji family (an illegitimate branch of the Ryūzōji clan). He sent his own son, Ryūzōji Kaneie, to be adopted by Iekado and received a daughter (later known as Keiginni) from Ryūzōji Tanekazu, the sixteenth head of the Muranaka-Ryūzōji family (the main branch of the clan) to wed Kaneie.
In 1545, Iesumi was assassinated by Baba Yorichika, a senior retainer of the Shōni who feared the growing influence of the Ryūzōji family. According to another theory, he died in battle against Kumashiro Katsutoshi incited by Yorichika. Alternatively, he was killed while attempting to flee.