The Lahn is a 245.6-kilometer (152.6 mi)-long, right (or eastern) tributary of the Rhine in Germany.
Its course passes through the federal states of North Rhine-Westphalia (23.0 km), Hesse (165.6 km), and Rhineland-Palatinate (57.0 km).

The Lahn originates at the Lahnhof, a locality of Nenkersdorf, which is a constituent community of Netphen in southeastern North Rhine-Westphalia, near the border with Hesse.
The source area is situated along the Eisenstraße scenic highway and the Rothaarsteig hiking trail.

The river arises in the southeastern Rothaargebirge in the Ederkopf-Lahnkopf-Rücken ridge-line natural area.
This ridge is the drainage divide between the Rhine and Weser, and, within the Rhine system, the watershed between the rivers Lahn and Sieg.

The source is at an elevation of 600 meters (2,000 ft) and is located southwest of the 624 m (2,047 ft) high Lahnkopf.
In the vicinity are also the origins of the Eder (5.5 km northwest of the Lahnhof) and the Sieg (another 3 km north).
Whereas the Sieg takes the shortest route to the Rhine (to the west), the Lahn first runs in the opposite direction, paralleling the Eder for many kilometers.
The Lahn is a 245.6-kilometer (152.6 mi)-long, right (or eastern) tributary of the Rhine in Germany. Its course passes through the federal states of North Rhine-Westphalia (23.0 km), Hesse (165.6 km), and Rhineland-Palatinate (57.0 km).
The Lahn originates at the Lahnhof, a locality of Nenkersdorf, which is a constituent community of Netphen in southeastern North Rhine-Westphalia, near the border with Hesse. The source area is situated along the Eisenstraße scenic highway and the Rothaarsteig hiking trail.
The river arises in the southeastern Rothaargebirge in the Ederkopf-Lahnkopf-Rücken ridge-line natural area. This ridge is the drainage divide between the Rhine and Weser, and, within the Rhine system, the watershed between the rivers Lahn and Sieg.
The source is at an elevation of 600 meters (2,000 ft) and is located southwest of the 624 m (2,047 ft) high Lahnkopf. In the vicinity are also the origins of the Eder (5.5 km northwest of the Lahnhof) and the Sieg (another 3 km north). Whereas the Sieg takes the shortest route to the Rhine (to the west), the Lahn first runs in the opposite direction, paralleling the Eder for many kilometers.
Lahn