Saitō Toshinaga (斎藤 利永, died June 16, 1460) was a Japanese daimyo during the Muromachi period.
To support his father, Toshinaga built Izumii Castle[1] to serve as the base for the Saitō clan.
When Sōen was assassinated in 1450, Toshinaga assumed control of the clan and became the shugo of the province.
Mochimasa's grandson, who was only three years old at the time, was nominated to be the successor, but Toshinaga objected.
Toshinaga died a few years later in 1460 from complications related to paralysis.