Lifespan: Eishō 2 (1505) to 8/15 of Eiroku 9 (1566)
Clan: Okabe (descended from the Kudō clan of the Fujiwara-Nanke)
Lord: Imagawa Ujizane
Siblings: Ōuba-no-tsubone, Nagatsuna, Sadatsugu
Okabe Sadatsuna served as a bushō during the Sengoku period.
Sadatsuna was a retainer of Imagawa Ujizane, the sengoku daimyō and twelfth head of the Imagawa clan of Suruga Province.
In 1568, the Okabe clan formed a part of the Takeda navy during the Invasion of Suruga by Takeda Shingen, the sengoku daimyō and nineteenth head of the Kai-Takeda clan of neighboring Kai Province.
During the early Edo period, Sadatsuna’s eldest son, Okabe Nagatsuna, later served Tokugawa Ieyasu as a hatamoto, or direct retainer of the shōgun, receiving a fief of 1,500 koku. Sadatsuna’s daughter wed Kawamura Shigetada and, after the death of her husband, served the Tokugawa, becoming the nursing mother of Tokugawa Hidetada. She was called Ōuba-no-tsubone.