Laudach is a river in the Austrian state of Upper Austria. With the outer Laudach, the river reaches a length of something over 20 km (12 mi). The Laudach is a left and the main tributary of the Alm.
The longer, äußere (outer) Laudach is the output of the Laudachsee in Gmunden. It passes the city areas of Sankt Konrad, Gschwandt, Kirchham and Vorchdorf from the south.
The smaller tributary, the innere or dürre (inner) Laudach, has its source in the municipality of Kirchham. It forms from two sources, the "Platzbach" and the "Edlbach". The water stems from three hills (Wiesberg, Hacklberg and Feichtenberghills) that lay like a horse shoe around the village Hagenmühle in Kirchham. This right tributary discharges from the south into the "äußere" Laudach north of the center of Vorchdorf.
The Laudach empties into the Alm River about 5 km (3.1 mi) after the junction of the äußeren and inneren Laudach, several times interrupted by small weirs, in the southern area of the city of Bad Wimsbach.
There are a couple of artificial applied ponds alongside the Laudach.