| Grundwasser | |
| Source1 Location: | Kottmar |
| Mouth Coordinates: | 50.9693°N 14.7114°W |
| Progression: | Landwasser→ |
| Subdivision Type1: | Country |
| Subdivision Name1: | Germany |
| Subdivision Type2: | States |
| Subdivision Name2: | Saxony |
| Length: | 3.2miles |
The Grundwasser, also called Grundbach or Hinteres Wasser, is a small stream of Upper Lusatia in Germany. It is a left tributary of the Landwasser, which it joins near Oderwitz. It has a length of about three miles and flows through the villages Eibau and Oderwitz.