The Rotbach (in its upper reaches it is called the Zartenbach and Löffeltalbach, in its middle section, the Höllenbach) is the 19.9-kilometre-long, left-hand and southeasterly headstream of the Dreisam in the Southern Black Forest in the south German state of Baden-Württemberg.

The headstreams of the upper reaches of the Rotbach, known as the Zartenbach, begin on the territory of Hinterzarten (Southern Black Forest Nature Park) southwest of the village of Oberzarten on the eastern mountainside of the Ramselehöhe (1,111,9 m) at about 1,085 metres above sea level.

After picking up the outflow of the western part of the moor, the stream deepens as it enters a V-shaped valley and descends steeply.

The stream, now called the Höllenbach, flows northwest initially through the straight trough valley of the upper Höllental which was formed by ice age glaciers.

In the lower section of the valley, the stream continues as the Rotbach through Falkensteig and Himmelreich (villages in the municipality of Buchenbach), where it flows out into the plain of the Zarten Basin.