The source of the Ruhr is near the town of Winterberg in the mountainous Sauerland region, at an elevation of approximately 670 metres (2,200 ft).

Its total length is 219 km (136 mi), its average discharge is 79 cubic metres per second (2,800 cu ft/s) at Mülheim near its mouth.

The Ruhr first passes the towns of Meschede, Arnsberg, Wickede, Fröndenberg, Holzwickede, Iserlohn, and Schwerte.

Then the river marks the southern limit of the Ruhr area, passing Hagen, Dortmund, Herdecke, Wetter, Witten, Bochum, Hattingen, Essen, Mülheim, and Duisburg.

The occupation of the Ruhr from 1923 to 1924 by French forces, due to the Weimar Republic's failure to continue paying reparations from World War I, provoked passive resistance, which saw production in the factories grind to a halt.