This article is about the expressionist painter from Silesia. For the painter of the same name from Halle, Saxony-Anhalt, see Otto Müller (painter). For other people named Otto Mueller, see Otto Müller.
During World War I he fought as a German soldier in France and Russia. After the war he became a professor at the academy of arts (Akademie der Bildenden Kunste) in Breslau where he taught until his death on 24 September 1930. Johnny Friedlaender and Isidor Ascheim were among his pupils there.
In 1937 the Nazis seized 357 of his works from German museums, since the pictures were considered to be degenerate art.
Mueller was one of the most lyrical of German expressionist painters. The main topic of Mueller's works is the unity of humans and nature; his paintings emphasize a harmonious simplification of form, colour and contours. He is known especially for his characteristic paintings of nudes and Romani (Gypsy) women; his nickname was "Gypsy Mueller" and his mother was perhaps Romani. The medium he preferred for his paintings was distemper on coarse canvas, which produced a mat surface. Altogether his printmaking amounted to 172 prints, nearly all of them lithographs, but including a few woodcuts and etchings.