Tosa han

• Japanese: 土佐藩 (Tosa han)
• Other Names: 高知藩　(Kouchi han)
• Territory: Tosa province
• Castle: Kôchi castle
• Lords: Yamauchi clan
• Kokudaka: 200,000

Tosa was a prominent tozama and kunimochi domain located on the island of Shikoku. The 200,000 koku domain was ruled by the Yamauchi clan from Kôchi castle, its territory roughly coterminous with Tosa province.

Tosa is of particular significance in Bakumatsu and Meiji Period politics as one of the chief domains (along with Satsuma and Chôshû) from where many of the most prominent anti-bakufu shishi rebels, i.e. Imperial loyalists emerged. Prominent Tosa figures from that period include Sakamoto Ryôma, Yoshida Tôyô, Itagaki Taisuke, and Takechi Zuizan. Tosa is also significant as the domain which, while Satsuma and Chôshû were preparing for war, presented Shogun Tokugawa Yoshinobu with a petition requesting that he step down; though in the end there was some considerable fighting in the lead-up to the Meiji Restoration and its immediate aftermath, in truth, the last shogun was not forced to resign at swordpoint, but rather accepted this Tosa petition and gave up his position willingly and relatively peacefully.

Edo Period

The domain's governance and laws were based, in part, on the "100 Article Code of the Chosokabe," written by the Chôsokabe clan who ruled Tosa prior to the Yamauchi.

A particular type of Japanese long-tailed fowl called the onagadori was specially bred in Tosa, and its feathers were often used to decorate spears used in the lord's sankin kôtai processions, adding to the distinctiveness of Tosa's processions.

According to one account, Tosa was during the Edo period one of the strictest domains in terms of allowing individuals in and out of its borders, with only Satsuma, Awa, and Hizen han being identified as more tightly "closed."

Lords of Tosa

1. Yamauchi Kazutoyo (d. 1605)
2. Yamauchi Tadayoshi (1592-1664)

...

1. Yamauchi Toyoteru (d. 1848)
2. Yamauchi Toyoatsu (1825-1854)
3. Yamauchi Toyoshige (aka Yamauchi Yodo, 1827-1872)