Sulu Archipelago (sōō´lōō), island group, 1,086 sq mi (2,813 sq km), the Philippines, SW of Mindanao. Lying between the Celebes and Sulu seas, it includes over 900 volcanic islands and coral islets extending almost to Borneo. Basilan is the largest island, Jolo the most important. Fishing is the major source of livelihood; the Sulu Sea supplies a large proportion of the nation's commercial catch. The archipelago is also the prime source for pearls, marine turtles, seashells, and sea cucumbers. The islands are heavily forested, but local farming is nonetheless carried on and meets the needs of the people. Large quantities of manioc (a root staple) are grown.

The inhabitants are Moros, a Malayan people who were converted when Islam spread from Malaya and Borneo in the 14th and 15th cent. Formerly notorious as pirates, the Muslim Moros resisted Spanish rule until the 19th cent. The Sultanate of Sulu (est. in the 16th cent. and also including Sabah in what is now Malaysia) passed to U.S. control in 1899 and continued to flourish under a mutually advantageous treaty with the United States. In 1940 the sultanate was abolished and Sulu became part of the Philippine Commonwealth, although most Moros rejected Manila's authority. In 1976 the government reached a cease-fire agreement with Moros rebels, calling for the creation of an autonomous region including the Sulu Archipelago. However, such a region was not established until 1990. Fundamentalist groups in the area continue to press for an independent Islamic state.