Diest is a city and municipality located in the Belgian province of Flemish Brabant. It is situated in the northeast of the Hageland region, approximately 60 km from Brussels. The city neighbors the provinces of Antwerp to its north and Limburg to its east.
The municipality encompasses the city of Diest proper along with the towns of Deurne, Kaggevinne, Molenstede, Schaffen, and Webbekom. As of January 1, 2006, the area had a total population of 22,845 residents across a total area of 58.20 km², resulting in a population density of 393 inhabitants per km².