Querrien (; ) is a commune in the Finistère department of Brittany in northwestern France.
Inhabitants of Querrien are called in French Querriennois.
The village centre is located north of Quimperlé.
Querrien is border by Lanvénégen to north, by Meslan and Locunolé to east, by Tréméven and Mellac to south and by Saint-Thurien to west.
The municipality launched a linguistic plan concerning the Breton language through Ya d'ar brezhoneg on 7 March 2007.