| White Ernz | |
| Subdivision Type1: | Country |
| Length: | 30km (20miles) |
The White Ernz is a river flowing through Luxembourg, joining the Sauer at Reisdorf. It flows through the towns of Larochette, Medernach and Ermsdorf. The river valley also includes the notable feature of having a twin castle from the 14th century named Larochette Castle.[1] It gives its name to the commune of Vallée de l'Ernz, formed in 2012 through the fusion of Medernach and Ermsdorf.