Opwijk (Dutch pronunciation:[ˈɔpʋɛi̯k]) is a municipality located in the Belgian province of Flemish Brabant. The municipality comprises the towns of Mazenzele and Opwijk proper. On January 1, 2012, Opwijk had a total population of 13,990. The total area is 19.69 km2 which gives a population density of 690 inhabitants per km2.