The Windauer Ache is a mountain stream in Tyrol, Austria, in the scenic Windautal valley in the Kitzbühel Alps.

The Ache rises on the Reinkarsee at about 2,200 m (AA), at the foot of the Kröndlhorn, and its middle reaches run through a roughly 4 km (2.5 mi) long gorge.

At the end of July 2006, a severe storm caused enormous damage throughout the entire Windau valley.

The flood of the Windauer Ache tore away the stream shoring, bridges and road sections.

The investment sum for the restoration - and simultaneous shoring and regulation of the river - amounted to approximately 860,000 euros.