Borneo is the third largest island in the world and is located at the centre of Maritime Southeast Asia.
Indonesians refer to the entire island as Kalimantan. Malaysians usually refer to the island by the names of either of its two Malaysian states, Sarawak and Sabah. The independent nation of Brunei occupies the remainder of the island.
Source: Wikipedia (under GNU Free Documentation License)
Borneo is surrounded by the South China Sea to the north and northwest, the Sulu Sea to the northeast, the Celebes Sea and the Makassar Strait to the east and the Java Sea and Karimata Strait to the south. It has an area of 743,330 square kilometres (287,000 sq mi).
To the west of Borneo are the Malay Peninsula and Sumatra. To the south is Java. To the east is the island of Sulawesi (Celebes). To the northeast is the Philippines.
Borneo’s highest point is Mount Kinabalu in Sabah, Malaysia, with an elevation of 4,095 m (13,440 ft) above sea level. This makes it the world’s third highest island.