The Ruhr, by German-speaking Anglo-American geographers and historians more accurately called the Ruhr district, Ruhr region or Ruhr valley (German Ruhrgebiet, colloquial Ruhrpott, Kohlenpott, Pott or Revier), is an urban area in North Rhine-Westphalia, Germany.

With a population density of 2,800/km² and a population of some five million, it is the largest urban agglomeration in Germany. It consists of several large, industrial cities bordered by the rivers Ruhr to the south, Rhine to the west, and Lippe to the north. In the Southwest it borders the Bergisches Land. It is considered part of the larger Rhine-Ruhr metropolitan region of more than 12 million people.

The biggest city in the Ruhr by area and population is Dortmund. From west to east, the region includes the cities of Duisburg, Oberhausen, Bottrop, Mülheim an der Ruhr, Essen, Gelsenkirchen, Bochum, Herne, Hagen, Dortmund, and Hamm, as well as parts of the more "rural" districts of Wesel, Recklinghausen, Unna and Ennepe-Ruhr-Kreis. Historically, the western Ruhr towns, such as Duisburg and Essen, belonged to the historic region of the Rhineland, whereas the eastern part of the Ruhr, including Gelsenkirchen, Bochum, Dortmund and Hamm, were part of the region of Westphalia. Since the 19th century, these districts have grown together into a large complex with a vast industrial landscape, inhabited by some 7.3 million people (including Düsseldorf and Wuppertal).