The Vilaine (French pronunciation: [vilɛn] ⓘ; Breton: Gwilen) is a river in Brittany, in the west of France.

[1] 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:[citation needed] They are also amenities for recreational activities.

The river has a flow ranging between 2 and 1500 m3/s[citation needed] The Vilaine is part of Brittany's canal system, built mainly in the 19th century for relatively small barges (130 tonnes).