The Saar (French: Sarre) 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 (the Sarre Rouge and Sarre Blanche, which join in Lorquin), that both start near Mont Donon, the highest peak of the northern Vosges. After 246 km (126 km in France and 120 km in Germany) the Saar flows into the Moselle at Konz (Rhineland-Palatinate) between Trier and the Luxembourg border. It has a catchment area of 7 431 km².
The Saar was very important for the Saarland coal, iron and steel industries. Raw materials and finished products were shipped on it by water via the Canal des houillères de la Sarre, the Marne-Rhine Canal and the Rhine, for instance, to the Ruhr area or the port of Rotterdam.
Although the German part of the Saar has been upgraded to a waterway by deepening, construction of sluices and straightening, there is no significant shipping traffic.