The Hosokawa clan was a powerful shugo daimyo in Japan. The Hosokawa clan ruled Awa, Awaji, Bitchu, Izumi, Sanuki, Settsu, Tamba, Tosa, and Yamashiro Provinces. The Hosokawa clan was one of the San-Kanrei, meaning three butlers, in Ashikaga shogunate. Hosokawa Katsumoto, the fifth, fought in the Onin War. His son, Hosokawa Masamoto , took dictatorial power in Ashikaga shogunate but, in a succession dispute, he was assassinated in 1507. After his death, the Hosokawa clan divided and the factions fought each other; their power weakened.

For a time they lived in the Hosokawa Gyobutei, a mansion in Kumamoto which was constructed in 1646. It is located near Kumamoto Castle. Both the castle and the mansion are now tourist attractions, and the mansion has guided tours of the mansion grounds and relics. Among the relics is a tea cup used by the protagonist of the story of the Forty-seven Ronin.

Former Prime Minister Morihiro Hosokawa is a descendant of the Hosokawa clan.