On the island of Borneo, Malaysia's East Malaysia region shares a land border with Indonesia and which other country?

The correct answer is Brunei, a small, oil- and gas-rich sultanate located on the northern coast of Borneo, entirely surrounded by Malaysia's Sarawak state except for its coastline along the South China Sea. Brunei is effectively split into two disconnected parts by a strip of Sarawak territory that separates the Temburong district from the rest of the country, making the Malaysia-Brunei border geography particularly intricate and a distinctive feature of Borneo's political map. Together, Indonesia, Malaysia, and Brunei form the three sovereign nations that divide Borneo, the world's third-largest island, with Indonesia's Kalimantan occupying roughly three-quarters of the island's area, Malaysia's Sabah and Sarawak covering most of the remainder, and Brunei occupying a much smaller enclave-like territory. Despite its small size, Brunei is notable for its substantial oil and natural gas wealth, giving it one of the highest per-capita incomes in Southeast Asia. Philippines is incorrect because, although it is a nearby archipelagic nation in maritime Southeast Asia, it does not share any part of Borneo and has no land border with Malaysia; its closest connection is via the Sulu and Celebes Seas. Singapore is incorrect since it is a small island city-state at the southern tip of the Malay Peninsula, connected to Peninsular Malaysia by causeways, not located on Borneo at all. Timor-Leste is incorrect because it lies far to the southeast on the island of Timor, bordering Indonesia, and has no geographic connection to Borneo or Malaysia. A common exam confusion is assuming the Philippines, being geographically close and part of the Malay-influenced region, borders Malaysia on Borneo, when in fact it shares only maritime proximity, not a land or island-sharing border. Revision takeaway: Borneo is shared by exactly three countries — Indonesia, Malaysia, and Brunei — with Brunei almost entirely enclosed within Malaysia's Sarawak.