The Museum Ostwall is a museum of modern and contemporary art in Dortmund, Germany. It was founded in the late 1940s, and has been located in the Dortmund U-Tower since 2010. The collection includes paintings, sculptures, objects and photographs from the 20th century, plus over 2,500 graphics, spanning Expressionism through classic modern art to the present day.

Dortmund is the third-largest city in North Rhine-Westphalia, after Cologne and Düsseldorf, and the ninth-largest city in Germany. With a population of 612,065 inhabitants, it is the largest city of the Ruhr as well as the largest city of Westphalia. It lies on the Emscher and Ruhr rivers in the Rhine-Ruhr Metropolitan Region, the second biggest metropolitan region by GDP in the European Union, and is considered the administrative, commercial, and cultural centre of the eastern Ruhr. Dortmund is the second-largest city in the Low German dialect area, after Hamburg.