The Otterbach is a stream, 42 kilometres long, in South Palatinate in the German state of Rhineland-Palatinate, that flows eastwards and northeastwards towards the Upper Rhine.

After breaking out of the low mountain range into the Upper Rhine Valley, the Otterbach flows through the two villages named after it, Oberotterbach and Niederotterbach, then through Vollmersweiler and Freckenfeld, where it passes the northern edge of the Bienwald woods.

In Minfeld it is joined from the left by the Dierbach, and then forms the border between the districts of Kandel and Wörth.

After it has passed through Neupotz, it is impounded southeast of Leimersheim to form the Fischmal, a reservoir 1½ kilometres long and up to 100 metres wide that is a biotope for many aquatic birds and plants.

Whilst some of the Otterbach's waters are diverted to the right through a pumping station on the Rhine embankment directly into the Rhine itself, the left-hand branch of the river flows through the village of Leimersheim and is united there with the Erlenbach coming from the left to form the Michelsbach.