| Vilaine | |
| Pushpin Map: | France#France Bretagne |
| Source1 Location: | Juvigné, Mayenne |
| Source1 Coordinates: | 48.2294°N -1.0531°W |
| Mouth Location: | Atlantic Ocean |
| Mouth Coordinates: | 47.5056°N -2.4992°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | France |
| Length: | 218.1km (135.5miles) |
| Source1 Elevation: | 175m (574feet) |
| Discharge1 Avg: | 80m3/s |
| Basin Size: | 10882km2 |
The Vilaine (in French pronounced as /vilɛn/; Breton: Gwilen) is a river in Brittany, in the west of France. The river's source is in the Mayenne département (53), and it flows out into the Atlantic Ocean at Pénestin in the Morbihan département (56). It is 218 km long.
The river arises near the towns of Juvigné and La Croixille. It passes through 4 départements (Mayenne, Ille-et-Vilaine, Loire-Atlantique and Morbihan) and 4 main towns (Rennes, Vitré, Redon, and La Roche-Bernard), then flows into the Bay of Biscay by Pénestin.
Three barrages were built around Vitré, Ille-et-Vilaine to alleviate flooding, while securing potable water supplies:
They are also amenities for recreational activities.
The river has a flow ranging between 2 and 1500 m3/s
The Vilaine is part of Brittany's canal system, built mainly in the 19th century for relatively small barges (130 tonnes). The entire system was transferred to the Brittany Region in 2011. In Rennes the river connects to the Canal d'Ille et Rance hence the Rance estuary, which enters the English Channel at Saint-Malo. In Redon it crosses the Canal de Nantes à Brest, giving access to Pontivy and the Blavet (west) and Nantes (east).
250 px|thumb|Vilaine catchment area