island group of the southeastern Moluccas, lying west of the Aru Islands and southeast of Seram, in the Banda Sea. The group, which forms part of Maluku provinsi (province), Indonesia, includes the Kai Besar (Great Kai), Kai Kecil (Little Kai) and Kai Dulah, and the Kur and Tayandu island groups. The Kai Islands' total land area is 555 square miles (1,438 square km). Kai Besar is mountainous, rising to nearly 3,000 feet (900 metres); it has steep cliffs along the coasts. Most of the islands are encircled by shoals, and all are covered with dense forest, a source of timber.

Flora include the fig and the ironwood tree and various palms and mangrove; rice and tobacco are cultivated. Among the fauna are a wild pig and a small, pouched mammal called a cuscus. Numerous tortoises are found on the reefs.

The inhabitants are typical black Papuans who have intermarried considerably with peoples of Malay stock. Because of missionary work, they are now predominantly Christian, but there are many Muslims. The society is communal in organization, untilled land being owned by the village and cultivated ground by the individual as long as he tills it. Kai Islanders are skillful at wood carving and basketry and are first-class boatbuilders. Plantain, yams, corn (maize), rice, and tobacco are grown. Two communities, Banda Elat on the western coast of Kai Besar and Banda Eli on the eastern coast, represent the original inhabitants of the Banda Islands driven away from their home islands by the Dutch in the early 17th century. The principal trade is in copra, timber, trepang, and tortoiseshell. Tual, on the western coast of Kai Kecil, is the administrative centre and main port. Pop. (2000 est.) 74,000.