| Dornbirner Ach | |
| Map: | Dornbirner Ache.png |
| Subdivision Type1: | Country |
| Source1 Coordinates: | 47.3074°N 9.7678°W |
| Mouth Coordinates: | 47.4985°N 9.6754°W |
| Length: | 29.9 km |
| Source1 Elevation: | 1485 m |
| Mouth Elevation: | 385 m |
| Basin Size: | 223 km2 |
The Dornbirner Ach (also called Dornbirner Ache) is a long stream in Vorarlberg, Austria, and a tributary of Lake Constance (German: Bodensee) and the Rhine, respectively. It flows through two gorges in its upper part, the Alploch Gorge and the Rappenloch Gorge.
The river's source is located in the mountains near the alpine village of (Dornbirn). Downstream, the river flows through one of the largest and most gorgeous gorges in Central Europe, the (en|Alploch Gorge) and (en|Rappenloch Gorge), which are separated by a small reservoir lake (German: Staufensee). Further downstream, the river cuts through the town of Dornbirn and then meanders off over a broad meadow landscape, the in the Alpine Rhine Valley, finally flowing into Upper Lake Constance.
The mouth of the river was originally near Fussach, but since the straightening of the Alpine Rhine, it flows parallel and quite close to the latter into Lake Constance near Hard.[1] Its mouth lies west of the Bregenzer Ach.
Some of its tributaries are the Kugelbach, Bruderbach, Spätenbach, Gunzenach/Kobelach and Schwarzach.
