Marne (French pronunciation: [maʁn]) is a department in the Grand Est region of France.

The Battles of the Marne, where the British and French fought against Germany during World War I, took place here.

Marne is part of the region of Grand Est and is surrounded by the departments of Ardennes, Meuse, Haute-Marne, Aube, Seine-et-Marne, and Aisne.

Geologically, it divides into two distinct parts; the Upper Cretaceous chalk plain in the east and the more wooded and hilly Eocene and Oligocene in the west.

Rivers draining the department include the Marne, Vesle, Ardre and Somme-Soude.