Lennik () is a municipality located in the Belgian province of Flemish Brabant. The municipality comprises the towns of Sint-Kwintens-Lennik, Sint-Martens-Lennik, Eizeringen and Gaasbeek. It is also situated in the Pajottenland. On January 1, 2006, Lennik had a total population of 8,694. The total area is 30.80 km<sup>2</sup> which gives a population density of 282 inhabitants per km<sup>2</sup>.
On its territory is the national Gaasbeek Castle museum. A 4 metre high statue of Prince (a Belgian Draught, draught horse) stands on the Market Place.