- Birth: 1510
- Death: 1582
- Distinction: Tokugawa retainer
- Sons: Okubo Tadayo, Okubo Tadasuke, Okubo Tadatame (1554-1616), Okubo Tadataka (1560-1639)
Tadakazu was a son of Okubo Tadahiro. He served Matsudaira Hirotada and Tokugawa Ieyasu and was active in the latter's struggles against the monto of Mikawa after 1561. While the young Ieyasu was a hostage of the Imagawa, Tadakazu worked effectively to help keep his clan together in his absence.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005