In Japanese history, the Yamauchi or Yamanouchi family were a family of rulers over what was then the Tosa Province which spanned the southern half of Shikoku island.
The province was gifted to the family in 1600 after Yamauchi Kazutoyo led troops under Tokugawa Ieyasu at the Battle of Sekigahara. The family stayed loyal to the Tokugawa dynasty until shortly before its overthrow in 1868. The head of the family at that time Yamauchi Toyoshige became prince of the newly formed Kochi Prefecture under Imperial rule.