| Type: | Stadtteil |
| Town: | Schwanebeck |
| Nienhagen | |
| Coordinates: | 51.95°N 21°W |
| State: | Sachsen-Anhalt |
| District: | Harz |
| Elevation: | 94 |
| Area: | 6.73 |
| Population: | 449 |
| Stand: | 2006-12-31 |
| Postal Code: | 39397 |
| Area Code: | 039403 |
Nienhagen is a village and a former municipality in the district of Harz, in Saxony-Anhalt, Germany. Since 1 January 2010, it is part of the town Schwanebeck.