| Ruins of Freudenau Castle | |
| Native Name: | Ruine Freudenau |
| Built: | around 1240 |
| Type: | lowland castle |
| Condition: | ruin |
| Location: | Untersiggenthal |
| Coordinates: | 47.5124°N 8.234°W |
| Map Type: | Canton of Aargau#Switzerland |
| Code: | CH-AG |
Freudenau Castle is a ruined fort in the municipality of Untersiggenthal of the Canton of Aargau in Switzerland. It is a Swiss heritage site of national significance.[1]