The White Ernz (Luxembourgish: Wäiss Iernz, French: Ernz blanche, German: Weiße 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.

This article related to a river in Luxembourg is a stub.