| Aa | |
| Mouth Location: | Möhne |
| Mouth Coordinates: | 51.4186°N 8.5831°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Germany |
| Subdivision Type2: | State |
| Subdivision Name2: | North Rhine-Westphalia |
| Source1 Elevation: | 459m (1,506feet) |
| Mouth Elevation: | 387m (1,270feet) |
| Pushpin Map: | North Rhine-Westphalia |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | North Rhine-Westphalia |
| Pushpin Map Alt: | Relief Map of North Rhine-Westphalia |
Aa is a river of North Rhine-Westphalia, Germany. It is 7.4km (04.6miles) long and is a left tributary of the Möhne[1] in Brilon. The river has a watershed of 23.071km2.
The source of Aa is in the village of Altenbüren. From here it flows in an easterly direction. At 473m (1,552feet) above sea level its course meanders to the north. Nearby the Hillbringse flows in from the south. Half a kilometer farther are five former mills in Aatal, called Aamühlen. The Fülsenbecke flows in near here from the north. The Aa overcomes an elevation difference of 72m (236feet), which corresponds to an average bed slope of 9.7 percent.