Amakusa Islands (ämäkōˈsä) [key], archipelago, c.340 sq mi (880 sq km), Kumamoto and Kagoshima prefectures, in the East China Sea, off W Kyushu, Japan. There are about 70 islands in the group. Shimo, the largest island, is the site of Hondo, which is the chief town. The interior of the islands is rugged; the coastal lowlands are fertile. Timber, oranges, fish, porcelain, and pearls are the principal products. Amakusa clansmen made the islands a major center of Christianity in the 16th cent. Villages and historical relics of this period are found in Unzen-Amakusa National Park.