Malaysia–Philippines border

The Malaysia–Philippines border is a maritime boundary located in the South China, Sulu and Celebes Seas. It separates the Malaysian state of Sabah, which is on the island of Borneo, and the Sulu Islands of the southern Philippines.

The boundary is the result of the division of the Sulu Sultanate through the cession of its territories to colonial powers. The British gained control of the northeast shores of Borneo, which became known as North Borneo and subsequently Sabah, while the rest of the Sulu Islands fell under Spanish control and later United States rule. The Philippines still officially claim the eastern part of Sabah as part of its territory, arguing the validity of the cession by the heirs of the Sultan of Sulu.

Malaysia and the Philippines are also parties to the multinational claims over the Spratly Islands and both countries have overlapping claims over some islands of the archipelago.

The historical connections of the people living on both sides of the border has resulted in the border being extremely porous, with a lot of illegal immigration from the Philippines occurring. The porous border has also resulted in several incidents of cross-border raids and kidnapping by armed groups from the Philippines on Malaysian towns and resorts on the east coast of Sabah.

The Malaysian–Philippine border consists of two segments. The first segment is the portion that has already been delimited through treaty. The second maritime segment has yet to be delimited because it is in the Spratly Islands area in the South China Sea where the two countries have overlapping claims over the continental shelf and islands.

Three treaties defined the territorial extent of the Philippine archipelago, of which two are relevant in terms of determining the boundary between Malaysia and the Philippines. The third treaty concerns the cession of some islands in the Sulu Sea but does not include any boundary determination clauses.

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