city, Ishikawa ken (prefecture), Honshu, Japan. It lies along the Kakehashi River, southwest of Kanazawa. Founded as a castle town in 1639, it was a post town during the Tokugawa period (1603–1867). Komatsu has been expanding since the late 19th century, and since 1919 copper-mining machinery, construction machinery, and tanks have been built there. In 1940 Komatsu was designated the central city of southern Ishikawa prefecture. The production of silk in Komatsu was eclipsed after World War II by the manufacture of synthetic fibres. Pop. (2005) 109,084.