Indonesia, country located off the coast of mainland Southeast Asia in the Indian and Pacific oceans. It is an archipelago that lies across the Equator and spans a distance equivalent to one-eighth of Earth’s circumference. Its islands can be grouped into the Greater Sunda Islandsof Sumatra (Sumatera), Java (Jawa), the southern extent of Borneo(Kalimantan), and Celebes (Sulawesi); the Lesser Sunda Islands (Nusa Tenggara) of Bali and a chain of islands that runs eastward through Timor; the Moluccas (Maluku) between Celebes and the island of New Guinea; and the western extent of New Guinea (generally known as Papua). The capital, Jakarta, is located near the northwestern coast of Java. In the early 21st century Indonesia was the most populous country in Southeast Asia and the fourth most populous in the world.