On which Caribbean island do France and the Netherlands share a land border?

France and the Netherlands share a land border on the Caribbean island of Saint Martin. The French northern part is the Collectivity of Saint Martin, while the southern part, Sint Maarten, is a constituent country within the Kingdom of the Netherlands.

The island covers about 87 square kilometres, divided roughly 60:40 between the French Republic and the Kingdom of the Netherlands. Their border is approximately 16 kilometres long and is generally open, so visitors can cross it without routine passport controls. Philipsburg lies on the Dutch side, while Marigot is the French administrative centre.

The division dates to the Treaty of Concordia, signed on 23 March 1648. France and the Netherlands formally partitioned the island after earlier disputes involving Spain and competing colonial claims. The island’s name causes confusion: “Saint Martin” commonly refers to the whole island in English, while “Sint Maarten” specifically identifies the Dutch side. Guadeloupe is entirely French and is not divided between the two countries.