The Saar is a river in northeastern France and western Germany, and a right tributary of the Moselle. It rises in the Vosges mountains on the border of Alsace and Lorraine and flows northwards into the Moselle near Trier. It has two headstreams, that both start near Mont Donon, the highest peak of the northern Vosges. After 246 kilometres (153 mi) the Saar flows into the Moselle at Konz (Rhineland-Palatinate) between Trier and the Luxembourg border. It has a catchment area of 7,431 square kilometres (2,869 sq mi).

The Moselle is a river that rises in the Vosges mountains and flows through north-eastern France and Luxembourg to western Germany. It is a left bank tributary of the Rhine, which it joins at Koblenz. A small part of Belgium is in its basin as it includes the Sauer and the Our.