Indonesia or Republic of Indonesia, the largest island nation in the world. It lies between the Indian and Pacific oceans off the mainland of Southeast Asia, occupying most of the Malay Archipelago. Indonesia extends some 3,200 miles (5,150 km) along the Equator and consists of nearly 13,700 islands. Celebes, Java, Sumatra, and Timor and portions of Borneo and New Guinea make up most of the country. The area is 735,358 square miles (1,904,569 km2)—roughly one-fifth that of the United States. Malaysia and Papua New Guinea are the only nations that border on Indonesia.

Separating the islands are numerous seas and straits, largest of which are the Banda, Celebes, Flores, Java, and Molucca seas. Some of the straits, especially the Strait of Malacca, are of great strategic importance.