The Attert (French pronunciation: [atɛʁt], German pronunciation: [ˈatɐt]; Luxembourgish: Atert) is a river flowing through Belgium and Luxembourg, left tributary of the Alzette. Its length is 38 kilometres (24 mi), of which 32 kilometres (20 mi) are in Luxembourg and 6 kilometres (4 mi) in Belgium. Its source is in Nobressart, north-west of Arlon, in the Belgian province Luxembourg. It flows into the river Alzette at Colmar-Berg. It flows through the village of Attert in Belgium, and the towns of Redange, Everlange, Useldange, Boevange-sur-Attert, and Bissen in Luxembourg.