Ōkubo clan

Ōkubo clan
Ōkubo clan crest
Home province	Mikawa
Parent house	Fujiwara clan via the Utsunomiya clan
Titles	daimyo, viscount
Founder	Ōkubo Tadatoshi
Final ruler	Ōkubo Tadayoshi (II)
Founding year	15th century
Dissolution	still extant
Ruled until	1873 (Abolition of the han system)
Cadet branches	four cadet branches to the Meiji Restoration

The Ōkubo clan (大久保氏, Ōkubo-shi^?) were a samurai kin group which rose to prominence in the Sengoku period and the Edo periods. Under the Tokugawa shogunate, the Ōkubo, as hereditary vassels of the Tokugawa clan, were classified as one of the fudai daimyō clans.

The Ōkubo clan traces its origins to 16th century Mikawa province. The Ōkubo claimed descent from the Utsunomiya clan, descendants of Fujiwara no Michikane (955–995). Ōkubo Tadatoshi (1499–1581) and his younger brother Ōkubo Tadakazu (1511–1583) were the first to abandon the Utaunomiya name for "Ōkubo". Both brothers were among the seven closest retainers of Matsudaira Hirotada, the father of Tokugawa Ieyasu.

The head of this clan, Ōkubo Tadanori line was ennobled as a viscount ("shishaku") in the kazoku peerage system.