The 88 square kilometer Caribbean island of Saint Martin/Sint Maarten has been divided between France and the Netherlands since the Treaty of Concordia in 1648. The boundary was shifted more than a dozen times between 1648 and 1816 by several different colonial powers before settling into its current alignment, which gives French Saint Martin the northern 62% of the island and Dutch Sint Maarten the southern 38%.

In 2023, France and the Netherlands resolved an old but uncontentious dispute between the two States over the sovereignty of Oyster Pond, a small inlet at the eastern end of the Saint Martin/Sint Maarten land boundary. As part of the same Agreement, more than four hundred boundary turning points were established, providing the first detailed boundary delimitation for Saint Martin/Sint Maarten.

While French Saint Martin is considered an outermost region of the European Union, Dutch Sint Maarten is not a European Union territory. Despite this, the 15.5 kilometer (9.6 mile) border is open and largely invisible on the ground.

Saint Martin and Sint Maarten also have an established maritime boundary.