Illhaeusern (; German: Illhäusern) is a commune in the Haut-Rhin department in Grand Est in north-eastern France. In the village, the river Ill receives the . Its name means "houses near the river Ill". Illhaeusern is famous for the Auberge de l'Ill, still one of the oldest 3-star establishments in France. It was managed until 2008 by Paul Haeberlin, his son Marc followed after his death.
