The Moosbach is a stream, approximately 6.6 kilometres (4.1 mi) long, in the South Palatine part of the Wasgau region in the German state of Rhineland-Palatinate.

About 300 metres (1,000 ft) downstream the Moosbach bends to the left and now flows in a northerly direction west of the Mehrsberg (328.2 m above NN).

Its calcareous grassland, wet meadows, intermediate bogs, dystrophic ponds with siltation zones, springs, streams, bushes and woods offer a multitude of species their own habitat, so that it forms one of the most important reserves in Südwestpfalz.

Alder grows in the carrs in the valley, albeit threatened at times by spruce and beech, and in the wet meadows deer fern, milk parsley, yellow flag and marsh marigold thrive.

Dragonflies and damselflies thrive greatly on the brown water ponds; a total of 37 different species have been identified in the valley, including the blue hawker.