Lahn may refer to:
- the Lahn, a river in western Germany
- Lahn, Hesse, a city that existed between 1977 and 1979 as a merger of Wetzlar and Gießen, in Hesse, Germany
- Lahn, Lower Saxony, a municipality in the district of Emsland, Lower Saxony
- Lahn (Wald im Pinzgau), a village in the municipality Wald im Pinzgau, Austria
- Lähn, German name of the town Wleń in Poland
Lahn is a dispersed settlement in the Oberpinzgau, the upper Salzach valley and the district of Zell am See/Pinzgau, and a village in the municipality of Wald im Pinzgau, on the southern rim of the Kitzbühel Alps.