Lifespan: Bunmei 14 (1482) to 11/13 of Meiō 8 (1499)
Other Names: Ōguromaru (childhood)
Father: Saitō Myōjun
Siblings: Toshichika, Matashirō, Hikoshirō, sister (wife of Asakura Sadakage), sister (wife of Kyōgoku Takakiyo), Toshitane
Wife: Daughter of the Ise-Nagano clan
Children: Ōguromaru (later known as Saitō Matashirō)
Saitō Matashirō served as a bushō during the Sengoku period.
Upon the death in battle of his father, Myōjun, and older brother, Saitō Toshichika, on 12/7 of Meiō 5 (1496), his nephew, Katsuchiyo (later known as Saitō Toshinaga) was still in his youth at the time so Matashirō became the fourth head of the Saitō-Jizein family. On 6/3 of Meiō 6 (1497), he attended his coming-of-age ceremony and adopted the name of Matashirō. He subsequently wed a daughter of the Ise-Nagano clan with whom the Saitō-Jizein were allies.
Matashirō suddenly died in 1499 at the age of eighteen. The headship of the clan was inherited by his younger brother, Saitō Hikoshirō.