Lahn spring, Natural spring in North Rhine-Westphalia, Germany.

The Lahn spring is a natural water source in the Rothaar Mountains of North Rhine-Westphalia, where the Lahn River begins its course. From this point, the water flows for several hundred kilometers before reaching the Rhine River near Lahnstein.

The Lahn River has been used for milling and trade since the Middle Ages, and its source in the Rothaar Mountains was already known to early settlers in the region. Over time, towns grew along the riverbanks, making the waterway central to the life of communities far from this starting point.

The name Lahn comes from an old Germanic word for slow-moving water, which fits the gentle way the river begins its course here. Hikers often stop at the spring to mark the starting point of a journey that follows the river downstream through several German states.

The spring sits along marked hiking trails in the Rothaar Mountains, with a small parking area near the hamlet of Lahnhof. Information panels at the site explain the river's origin and help orient visitors who want to continue along the trail network.

The spring pool, known as the Lahntopf, once served as a fire-fighting water pond for Lahnhof. In 2013 the outflow was opened up along 310 m, and the bridge on the path around the pool was replaced by stepping stones lying in the stream bed.