Bismarck Archipelago, island group of Papua New Guinea in the Bismarck Sea, southwestern Pacific Ocean, that lies northeast of the island of New Guinea. The largest components of the archipelago, which has a total land area of about 18,600 square miles (48,200 square km), are New Britain, New Ireland, the Admiralty Islands, New Hanover (Lavongai), and the smaller Duke of York Group, St. Matthias Group, and Witu (Vitu) Islands. The islands are generally volcanic or formed of raised coral limestone and are heavily forested.
Annexed by Germany in 1884, the archipelago was named for the German statesman Otto von Bismarck. The Germans developed copra plantations, but nonnative diseases carried by the Europeans killed many people on the islands. The archipelago was occupied by Australia in 1914 and made a mandated territory of Australia in 1920. The group was seized with little difficulty by Japan during World War II; Rabaul and other villages on the islands suffered heavy damage when Allied troops recaptured the area over the course of six weeks in 1944. The archipelago was subsequently made part of the UN Trust Territory of New Guinea, administered by Australia. When Papua New Guinea attained independence in 1975, the group became part of that country.
The economic mainstay of the islands is copra, with some lumbering and, more recently, cocoa and oil palm. Yams, sago, taro, bananas, and fish are the basic foods of the archipelago.