The Aubetin is a 61.2-kilometre (38.0 mi) long river in the Marne and Seine-et-Marne départements, northeastern France. Its source is at Les Essarts-le-Vicomte, 20 kilometres (12 mi) northeast of Nogent-sur-Seine. It flows generally west-northwest. It is a left tributary of the Grand Morin into which it flows at Pommeuse, 5 kilometres (3 mi) west of Coulommiers.