Fudai daimyō (譜代大名) was a class of daimyō (大名) in the Tokugawa Shogunate (徳川幕府) of Japan who were hereditary vassals of the Tokugawa before the Battle of Sekigahara. Fudai daimyō and their descendants filled the ranks of the Tokugawa administration in opposition to the tozama daimyō and held most of the power in Japan during the Edo period.

The Sakai clan was a Japanese samurai clan that claimed descent from the Nitta branch of the Minamoto clan, who were in turn descendants of Emperor Seiwa. Serata (Nitta) Arichika, a samurai of the 14th century, was the common ancestor of both the Sakai clan and the Matsudaira clan, which the Sakai later served. In the Sengoku period, under Tokugawa Ieyasu, the Sakai became chief retainers. In the Edo period, because of their longstanding service to the Tokugawa clan, the Sakai were classified as a fudai family, in contrast with the tozama.