| Exter | |
| Source1 Location: | Barntrup |
| Mouth Location: | Weser at Rinteln |
| Mouth Coordinates: | 52.1903°N 9.085°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Germany |
| Subdivision Type2: | States |
| Subdivision Name2: | Lower Saxony and North Rhine-Westphalia |
| Subdivision Type3: | Districts |
| Subdivision Name3: | Schaumburg and Lippe |
| Length: | 26.1km (16.2miles) |
| Mouth Elevation: | 274m (899feet) above NN |
| Basin Size: | 108.718km2 |
Exter is a long river in Lower Saxony (district Schaumburg) and North Rhine-Westphalia (district Lippe), Germany. It flows into the Weser in Rinteln.
The river arises from the eastern part of the district Lippe in the Teutoburg Forest / Egge Hills Nature Park. Its origin is in the municipality Barntrup, approximately one kilometre southwest of the northern district Alverdissen's centre, in an area used for agriculture.
It gave its name the municipality of Extertal (lit. Exter valley) that was founded newly in 1969.