The Chōsokabe clan (長宗我部氏 -shi) was a Japanese samurai clan of the Sengoku period, that controlled Tosa Province (Modern day Kōchi Prefecture), and later Shikoku Island. The clan is sometimes also known as Chōsokame (長曾我部). Chōsokabe Motochika, who unified Shikoku, was the 21st Daimyo (or head) of the clan.
The Chōsokabe clan is believed to have been descended from the Chinese emperor Qin Shi Huang, and were respected Jitô (deputy administrators) of Tosa from the 12th Century and entered the 16th Century as vassals of the Ichijô clan, who were based in western Tosa.
In their early history of the Sengoku Period, Chōsokabe Kunichika's father - Kanetsugu, was killed by the Motoyama clan in 1508. Therefore, Kunichika was raised by the aristocrat Ichijō Husaie of the Ichijō clan in Tosa Province. Later, towards the end of his life, Kunichika took revenge on the Motoyama clan and destroyed them with the help of the Ichijō in 1560. Kunichika would go on to have children - including his heir and the future Daimyo of the Chōsokabe - Motochika, who would go on to unify Shikoku Island.
First, the Ichijō family was overthrown by Motochika in 1574. Later, he gained control of the rest of Tosa due to his victories at the Battle of Watarigawa in 1575. He then also destroyed the Kono and the Soga clan. Over the ensuing decade, he extended his power to all of Shikoku in 1583. However, in 1585, Toyotomi Hideyoshi (Oda Nobunaga's successor) invaded that island with a force of 100,000 men, led by Ukita Hideie, Kobayakawa Takakage, Kikkawa Motonaga, Toyotomi Hidenaga, and Toyotomi Hidetsugu. Motochika surrendered, and forfeited Awa, Sanuki, and Iyo Provinces; Hideyoshi permitted him to retain Tosa.
Under Hideyoshi, Motochika and his son Chōsokabe Nobuchika participated in the invasion of neighboring Kyūshū, in which Nobuchika died. In 1590, Motochika led a naval fleet in the Siege of Odawara, and also fought in the Japanese invasions of Korea along with Toyotomi Hideyoshi in 1592.
After Motochika died in 1599 at age 61, his successor to the Chōsokabe was Chōsokabe Morichika.
The Chōsokabe lost their remaining lands (Tosa) after the Battle of Sekigahara in 1600 (The battle that essentially ended the Sengoku Period) to the Yamauchi. This was because, during the Sekigahara Campaign, the Chōsokabe were one of many clans who sided with the Western Alliance loyal to Toyotomi Hideyori (headed by Ishida Mitsunari and Mōri Terumoto) who were helping to fight against the Eastern Alliance (headed by Tokugawa Ieyasu). After the victory of the Tokugawa forces at the end of the Sekigahara campaign in 1600, Chōsokabe Morichika (the Daimyo) and the remaining retainers were beheaded because of their alliance with the Toyotomi, and the Yamauchi were given land in parts of Shikoku (including Tosa) because of their loyalty to the Tokugawa during the Sekigahara Campaign.
Among the retainers to the clan were Tani Tadasumi, Hisatake Chikanao, Yoshida Takayori, Yoshida Shigetoshi, Yoshida Masashige.
Shirō Sōkabe, the 19th century missionary, was a descendant of the Chōsokabe clan.