| Coordinates | 52°18′N 10°55′E |
|---|---|
| State | Niedersachsen |
| District | Helmstedt |
| Samtgemeinde | Grasleben |
| Elevation | 114 |
| Area | 22.6 |
| Postal code | 38368 |
| Area code | 05356 / 05365 |
| Licence | HE |
| Gemeindeschlüssel | 03 1 54 018 |
| Divisions | 3 |
| Website | www.grasleben.de |
| Mayor | Jörg Minkley |
| Party | CDU |
Rennau is a municipality in the district of Helmstedt, in Lower Saxony, Germany. The Municipality Rennau includes the villages of Ahmstorf, Rennau and Rottorf am Klei.