Mülheim, officially Mülheim an der Ruhr and also described as "City on the River", is a city in North Rhine-Westphalia in Germany. It is located in the Ruhr Area between Duisburg, Essen, Oberhausen and Ratingen. It is home to many companies, and two Max Planck Institutes.

The Ruhr, also referred to as the Ruhr area, sometimes Ruhr district, Ruhr region, or Ruhr valley, is a polycentric urban area in North Rhine-Westphalia, Germany. With a population density of 2,800/km2 and a population of over 5 million (2017), it is the largest urban area in Germany. It consists of several large 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 10 million people, which is the third largest in Western Europe, behind only London and Paris.