The Arnon is a 150.5 km (93.5 mi) long river in central France. It is a left tributary of the river Cher. Its source is near the village of Préveranges, west of Montluçon. Its longest tributary is the Théols. The Arnon flows generally north, through the following departments and towns:Allier Cher: Culan, Lignières, Chârost Indre: Reuilly