Rotselaar is a municipality located in the Belgian province of Flemish-Brabant, near the convergence of the Demer and the Dijle. Since January 1, 1977 the municipality comprises the towns of Rotselaar proper, Werchter and Wezemaal. On January 1, 2006, Rotselaar had a total population of 15,068. The total area is 37.57 km² which gives a population density of 401 inhabitants per km².