a South Korean island in the northern part of the East China Sea. Separated from the Korean Peninsula by the Cheju Strait and from the Japanese islands by the Korea Strait, the island occupies an area of 1,850 sq km.
The coast of Cheju-do consists mainly of cliffs that drop precipitously to the sea. The island is composed of volcanic rocks. The volcano Halla-san, which erupted in the tenth century, is located in the central part of Cheju-do; it has an elevation of 1,950 m. The island has a subtropical monsoon climate, with as much as 2,000 mm of precipitation a year. Evergreen and deciduous forests give way to coniferous forests at elevations higher than 1,600 m. Where forests have been felled, there are now meadows. Rice, barley, and the foxtail millet Setaria italica maxima are cultivated. Other economic activities include the catching of fish and mollusks. The city of Cheju is the capital of Cheju-do.