Montreuil (; ), distinguished as Montreuil-sur-Mer ("Montreuil-on-the-Sea") until 1945, is a commune in the Vendée Department in the Pays de la Loire region of western France.
Montreuil was the site of the 1299 Treaty of Montreuil, whereby the 1294âÂÂ1303 Gascon War between King EdwardI of England and PhilipIV of France was paused at Pope Gregory VIII's urging and a betrothal was arranged between Edward's son Prince Edward of Caernarfon and Philip's daughter Princess Isabella.