Denain (Picard: Dnain) is a commune in the Nord department in northern France. In 1999 Denain had a population of 20,360, on a land area of 11.52 km² (4.448 sq mi).It is the largest of 39 communes which comprise the association of communes of Porte du Hainaut, which in 1999 had a total population of 147,989.