Ōuchi clan (大内氏 Ōuchi-shi?) was one of the most powerful and important families in Japan during the reign of the Ashikaga shogunate in the 12th to 14th centuries descended of the king of Baekje on the Korean Peninsula. Their domains, ruled from the castle town of Yamaguchi, comprised six provinces at their height, and the Ōuchi played a major role in supporting the Ashikaga in the Nanboku-cho Wars against the Imperial Court. The Ōuchi remained powerful up until the 1560s, when they became eclipsed by their vassals, the Mōri clan.
Based in Suō Province, towards the western end of Honshū, the Ōuchi were among the primary families to be involved in foreign trade and relations, particularly with China. Following the Ōnin War (1467–1477), a strong rivalry developed between the Ōuchi and the Hosokawa family, who were now in power. The two clashed at Ningpo in 1523, and as a result the Chinese closed Ningpo to Japanese traders. By the time the Ōuchi were again allowed to send a ship a few years later, the trade was dying out. The family's trade with China fully came to an end by 1548, their monopoly broken by merchants from the seaport of Sakai. The Ōuchi also housed the Spanish Jesuit missionary Francis Xavier for a time in 1551.
As a result of their wealth and trading contacts, the Ōuchi gained renown in the worlds of art and culture as well. They possessed countless items of cultural and artistic significance and beauty, from Japan and China, as well as from further abroad. Particularly famous was the invitation by Ōuchi Masahiro of the famous painter Sesshū to Yamaguchi in 1486.
Significant members of the Ōuchi family
- Ōuchi Yoshihiro (1356–1400) – Led a revolt against Shogun Ashikaga Yoshimitsu.
- Ōuchi Masahiro – one of Yamana Sōzen's chief generals in the Ōnin War.
- Ōuchi Yoshioki (1477–1528) – Restored the shogun Ashikaga Yoshitane to power after a fifteen-year absence in 1508.
- Ōuchi Yoshitaka (1507–1551) – One of the first Ōuchi lords to see (and perhaps cause) the decline of the family.
- Ōuchi Yoshinaga (d. 1557) – The last Ōuchi lord, Yoshinaga committed suicide shortly after the Battle of Miyajima in which his family was defeated by the Mōri. He was the brother of Sengoku daimyo, Ōtomo Sōrin.
- Sansom, George (1961). A History of Japan: 1334–1615." Stanford: Stanford University Press.
- Sansom, George Bailey (1962). "Japan: A short cultural history." New York: Appleton-Century-Crofts, Inc.
- Turnbull, Stephen (1998). The Samurai Sourcebook. London: Cassell & Co.