Alsdorf is a municipality in the district of Aachen, in North Rhine-Westphalia, Germany. Until the 21st century Alsdorf was a mining area, but now many service companies have established themselves in Alsdorf. Besides, Alsdorf has an indoor arena, a cinema, a mining museum and a zoo. One of Alsdorf's famous sights is the old Castle.
Alsdorf may refer to the following places in Germany:
- Alsdorf, a town in the district of Aachen, North Rhine-Westphalia
- Alsdorf, Altenkirchen, a municipality in the district of Altenkirchen, Rhineland-Palatinate
- Alsdorf, Bitburg-Prüm, a municipality in the district of Bitburg-Prüm, Rhineland-Palatinate