Lennik is a municipality located in the Belgian province of Flemish Brabant. It is situated within the Pajottenland region and comprises several towns, including Sint-Kwintens-Lennik, Sint-Martens-Lennik, Eizeringen, and Gaasbeek.
The municipality covers a total area of 30.80 km2. As of January 1, 2006, Lennik had a total population of 8,694 residents, resulting in a population density of approximately 282 inhabitants per km2.