Indonesia–Malaysia border

The border between the Southeast Asian countries of Indonesia and Malaysia consist of both a land border separating the two countries' territories on the island of Borneo as well as maritime boundaries along the length of the Straits of Malacca, in the South China Sea and in the Celebes Sea.

The land boundary has a length of 2,019.5 km and stretches from Tanjung Datu at the northwestern corner of Borneo, through the highlands of the Borneo hinterland, to the Gulf of Sebatik and the Celebes Sea in the eastern side of the island. The boundary separates the Indonesian provinces of North Kalimantan, East Kalimantan and West Kalimantan, and the Malaysian states of Sabah and Sarawak.

The maritime boundary in the Straits of Malacca generally follows the median line between the baselines of Indonesia and Malaysian, running south from the tripoint with Thailand to the start of the maritime border with Singapore. Only part of this boundary has been delimited through a continental shelf boundary treaty in 1969 and a territorial sea boundary treaty in 1970. The continental shelf boundary between Indonesia and Malaysia in the South China Sea is also drawn along the equidistant line between the baselines of the two countries under the 1969 continental shelf boundary.

The border in the Celebes Sea is subject to dispute between the two countries. Part of the dispute was settled by the judgement of the International Court of Justice in the Ligitan and Sipadan Case in 2002 and is now awaiting delimitation between the two countries. The two countries however still have overlapping claims over the continental shelf which Indonesia refers to as Ambalat.

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