Arcos de Valdevez (Portuguese pronunciation:[ˈaɾkuʒ dɨ ˌvaɫdɨˈveʃ]) is a municipality along the northern frontier of Portugal and Galicia (Spain). The population in 2011 was 22,847, in an area of 447.60km². It is the largest municipality in area of the district of Viana do Castelo.