The island is politically divided among three countries: Malaysia and Brunei in the north, and Indonesia to the south. Approximately 73% of the island is Indonesian territory. In the north, the East Malaysian states of Sabah and Sarawak make up about 26% of the island. Additionally, the Malaysian federal territory of Labuan is situated on a small island just off the coast of Borneo. The sovereign state of Brunei, located on the north coast, comprises about 1% of Borneo's land area. A little more than half of the island is in the Northern Hemisphere including Brunei and the Malaysian portion, while the Indonesian portion spans both the Northern and Southern hemispheres.
The island is known by many names. Internationally it is known as Borneo, after Brunei, derived from European contact with the kingdom in the 16th century during the Age of Exploration. The name Brunei possibly derives from the Sanskrit word váruṇa (वरुण), meaning either "water" or Varuna, the Hindu god of rain. Indonesian natives called it Kalimantan, which was derived from the Sanskrit word Kalamanthana, meaning "burning weather island" (to describe its hot and humid tropical weather).
In earlier times, the island was known by other names. In 977, Chinese records began to use the term Po-ni to refer to Borneo or Brunei. In 1225, it was also mentioned by the Chinese official Chau Ju-Kua (趙汝适). The Javanese manuscript Nagarakretagama, written by Majapahit court poet Mpu Prapanca in 1365, mentioned the island as Nusa Tanjungnagara, which means the island of the Tanjungpura Kingdom.
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. To the west of Borneo are the Malay Peninsula and Sumatra. To the south and east are islands of Indonesia: Java and Sulawesi, respectively. To the northeast are the Philippine Islands. With an area of 743,330 square kilometres (287,000 sq mi), it is the third-largest island in the world, and is the largest island of Asia (the largest continent). Its highest point is Mount Kinabalu in Sabah, Malaysia, with an elevation of 4,095 m (13,435 ft). Before sea levels rose at the end of the last Ice Age, Borneo was part of the mainland of Asia, forming, with Java and Sumatra, the upland regions of a peninsula that extended east from present day Indochina. The South China Sea and Gulf of Thailand now submerge the former low-lying areas of the peninsula. Deeper waters separating Borneo from neighbouring Sulawesi prevented a land connection to that island, creating the divide known as Wallace's Line between Asian and Australia-New Guinea biological regions.