酒井氏
The 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 (who was the head of what was formerly the main Matsudaira family line), 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" ("outsider clans").