Shikoku (shĭkōˈkō) [key], island (1990 pop. 4,240,265), 7,247 sq mi (18,770 sq km), S Japan, separated from Honshu and Kyushu by the Inland Sea. The smallest of the major islands of Japan, its high mountains and steep slopes limit agriculture and impede communication; there are no volcanoes. Shikoku's climate is humid subtropical. Rice, grains, mulberry, palms, and camphor are the chief products. Fishing and salt production are important, along with the petroleum, metal, paper, and textile industries. A large copper mine is located at Besshi. Population is concentrated along the coast; Takamatsu and Matsuyama are the largest cities.