Brière (French pronunciation: [bʁijɛʁ] ⓘ; Breton: Ar Briwer) is the marsh area to the north of the Loire estuary in France at its mouth on the Atlantic Ocean.
The Brière marsh area includes a vast area of humid zones stretching from the Gulf of Morbihan and the estuary of the Vilaine to the north, to the salt marshes of Guérande to the west to the estuary of the Loire and the Lac de Grand-Lieu in the south.
It is rich in flora and fauna, and navigation is possible with boats called chalands.
Alphonse de Chateaubriant's prize-winning novel La Brière (translated as Passion and Peat), 1923, is set in the area and describes its traditions and culture.
It has been suggested that the small islands of the Brière, now joined by silt, could have been the location of the Cassiterides - islands mentioned in antiquity as the Phoenician source of tin.