Viļaka Castle (Latvian: Viļakas pilsdrupas) (Mariensee Castle, Marienhausen, Villack) is a castle in the historical region of Latgale, in eastern Latvia. The castle is located close to Viļaka town, on an island in the Viļaka Lake. Built by Archbishopric of Riga in 1342 as a wooden castle, rebuilt as a stone castle after 1516. The castle was destroyed in 1702 during the Great Northern War.