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 How to Make Millions Before Grandma Dies, known in Thai as Lahn Mah