| Lontzen | |
| Map: | Lontzen Liège Belgium Map.svg |
| Map-Legend: | Location of Lontzen in the province of Liège |
| Arms: | BE Lontzen COA.svg |
| Flag: | Flagge Lontzen.svg |
| Arrondissement: | Verviers |
| Nis: | 63048 |
| Mayor: | Patrick Thevissen (PFF, Energie) |
| Majority: | Energie, Ecolo |
| Postal-Codes: | 4710-4711 |
| Telephone-Area: | 087 |
| Web: | www.lontzen.be |
| Coordinates: | 50.6833°N 6°W |
Lontzen (pronounced as /de/) is a municipality located in East Belgium. On January 1, 2018 Lontzen had a total population of 5,695. The total area is 28.73 km2 which gives a population density of 198 inhabitants per km2.
The municipality consists of the following sub-municipalities: Lontzen proper, Herbesthal, and Walhorn.
In the 19th century, a Low Franconian dialect was widely spoken in Lontzen.