| Arz | |
| Pushpin Map: | France#France Bretagne |
| Source1 Location: | Plaudren |
| Source1 Coordinates: | 47.7431°N -2.7311°W |
| Mouth Coordinates: | 47.6558°N -2.1111°W |
| Subdivision Type1: | Country |
| Length: | 66.4km (41.3miles) |
| Source1 Elevation: | 130m (430feet) |
| Mouth Elevation: | 2m (07feet) |
| Discharge1 Avg: | 2.26m3/s |
| Basin Size: | 270km2 |
The Arz (Breton: Aer) is a 66.4km (41.3miles) long river in the Morbihan département, northwestern France. Its source is at Plaudren. It flows generally east-southeast. It is a right tributary of the Oust into which it flows at Saint-Jean-la-Poterie, near Redon.
This list is ordered from source to mouth: Plaudren, Monterblanc, Elven, Le Cours, Larré, Molac, Pluherlin, Malansac, Saint-Gravé, Peillac, Saint-Jacut-les-Pins, Saint-Vincent-sur-Oust, Allaire, Saint-Perreux, Saint-Jean-la-Poterie