Sakai-shi

Sakai clan 酒井氏
Emblem (mon) of the Sakai clan
Home province	Mikawa
Parent house	Nitta clan
Titles	Various
Founder	Sakai Chikauji
Founding year	14th century
Dissolution	still extant

The Sakai clan (酒井氏, Sakai-shi) 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").

The fudai Sakai clan originated in 14th century Mikawa Province. They claim descent from Minamoto no Arichika. Arichika had two sons; one of them, Yasuchika, took the name of Matsudaira, while the other son, Chikauji, took the name of Sakai. Chikauji is the ancestor of the Sakai clan. Sakai Hirochika, Chikauji's son, had two sons as well, and the descendants of these two sons gave rise to the two principal branches of the clan. The senior branch was founded by Sakai Tadatsugu (1527–1596). Tadatsugu, a vassal of Tokugawa Ieyasu, was charged with the defense of Yoshida Castle in Mikawa Province. In 1578, Sakai Ietsugu (1564–1619) succeeded to his father's role as defender of Yoshida Castle. The Ie- in the beginning of Ietsugu's name was a special honor bestowed by Tokugawa Ieyasu, who intended to emphasize bonds of loyalty with those who were allowed to share in any part of his name. When Ieyasu's holdings were transferred to the Kantō region in 1590, Ietsugu was installed at Usui Domain (30,000 koku) in Kōzuke Province, but, in 1604, he was moved to Takasaki Domain (50,000 koku). In 1616, he was again moved to Takada Domain (100,000 koku), this time in Echigo Province. In 1619, he was moved to Matsushiro Domain in Shinano Province; and then, from 1622 to 1868, he was installed at Tsuruoka Domain (120,000 koku) in Dewa Province. The Sakai of Tsuruoka (which later grew to 170,000 koku) in Dewa Province were prominent in the late Edo period as a military power. Charged with the safety of Edo, they were patrons of the Shinchogumi police force, and were very effective in their duties. Following the surrender of Edo, the Sakai withdrew and returned north to their domain, where they were active in the northern theater of the Boshin War, as well as becoming signatories to the pact that created the Ōuetsu Reppan Dōmei in 1868. The head of this clan line was ennobled as a "Count" in the Meiji period.