Eau Rouge
Red water (eau rouge in French) on the banks of the river
Location
Country	Belgium
Province	Liège
Physical characteristics
Source
• location	High Fens
Mouth
• location	Amblève
• coordinates	50°23′41″N 5°56′47″E / 50.3948°N 5.9464°E / 50.3948; 5.9464
Length	15 km (9.3 mi)
Basin features
Progression	Amblève→ Ourthe→ Meuse→ North Sea

The Eau Rouge is a small, 15-kilometre-long (9 mi) stream in the Belgian province of Liège. It is a right tributary of the Amblève.

It starts in the Hautes Fagnes ("High Fens") and ends in Challes, near Stavelot in the river Amblève. The French words eau rouge mean "red water", and the river gets its name from the reddish coloration of the stones and riverbed due to the presence of iron-oxide deposits. The Eau Rouge is particularly geomorphologically interesting,^{[according to whom?]} as it appears^[where?] to be using the old Warche river stream bed.^{[citation needed]}

The Eau Rouge has been a border river for several periods in its existence, including an administrative boundary under the Roman Empire between Cologne and Tongeren, and the state border between the Netherlands and Prussia from 1815 to 1839 and then between Belgium and Prussia from 1839 to 1919.

The Eau Rouge has lent its name to the Eau Rouge corner, one of the best-known corners in Formula One race tracks in the Circuit de Spa-Francorchamps motor racing circuit, at the point where the track crosses it for the first time.