cluster of 16 much-eroded high volcanic islands, Federated States of Micronesia, in the western Pacific Ocean. The name Chuuk means “high mountains” in the Chuukese language, one of several Malayo-Polynesian languages that are used in the islands. Forming part of the eastern Caroline Islands, the Chuuk Islands are enclosed within an encircling barrier bank composed of some 85 sand and coral islets. The bank (often referred to as a reef) encloses a lagoon 822 square miles (2,129 square km) in area and has a diameter of some 40 miles (65 km). Chief islands of the group are Weno (formerly Moen), Tonoas, Fefan, Uman, Uatschaluk (Udot), and Tol.

The islands were sighted by the Spanish explorer Álvaro Saavedra in 1528. The Chuuk Islands were visited occasionally by 19th-century traders and whalers and were included in the German purchase of parts of Micronesia from Spain (1899). Annexed by Japan (1914) and strongly fortified for World War II, the islands (known as the Truk Islands until 1990) were heavily attacked, bypassed, and blockaded by the Allies during the war. The sunken hulls of Japanese ships remain there, along with ruined weapons and fortifications on land. Together with the other islands in what are now the Federated States of Micronesia, the Chuuk group was part of the U.S.-administered United Nations Trust Territory of the Pacific Islands (Pacific Islands, Trust Territory of the) from 1947 to 1986.

The high islands of the Chuuk group have mangrove swamps along their coasts, as well as rainforests in the central mountainous areas. The native people are Micronesians (Micronesian culture) who fish, raise pigs and poultry, and grow taro, breadfruit, yams, and bananas. Copra is the chief cash crop. The islands are popular with scuba divers who come to explore the shipwrecks in the lagoon, many of which have become foundations for new reef growth. The largest urban area is on Weno; the rest of the population resides mostly in traditional villages scattered around the islands. Chuuk has a commercial dock and an international airport, both located on Weno. Total land area 38.5 square miles (100 square km). Pop. (2000) 40,465.