Borneo is the island shared by Brunei, Indonesia, and Malaysia.
Borneo is the world’s third-largest island and is divided politically among three countries. Malaysia controls the northern states of Sabah and Sarawak, Indonesia occupies most of the island in the region known as Kalimantan, and Brunei is a small independent sultanate on the northern coast.
The island’s political division developed through different colonial histories. British influence shaped northern Borneo, while the Netherlands controlled most of the southern and central areas before those territories became part of Indonesia. Brunei retained its sovereignty and became fully independent in 1984. The modern borders therefore reflect a mixture of colonial agreements, historical sultanates, and postcolonial state formation.
Borneo is also known for extraordinary biodiversity. Its rainforests support orangutans, proboscis monkeys, pygmy elephants, and many plant species found nowhere else. Mount Kinabalu, in Malaysia’s Sabah state, is the island’s highest peak at 4,095 metres.
Java, Sulawesi, and Sumatra are all Indonesian islands, but none is shared by these three countries. Borneo is the distinctive answer because it contains territory belonging to Malaysia, Indonesia, and Brunei.