Mortefontaine (French pronunciation: [mɔʁt(ə)fɔ̃tɛn]) is a commune in the Oise department in Northern France.

The 17th-century Château de Mortefontaine was bought by Joseph Bonaparte,[3] elder brother of Napoléon Bonaparte, in 1798.

The Convention of 1800 (also known as the Treaty of Mortefontaine), a friendship treaty between France and the United States, was signed in the castle.

The preliminaries of the 1802 Peace of Amiens were also negotiated there.

This Oise geographical article is a stub.