Eisenwerke Oberdonau (German for Steel Works of Upper Danube) was a large steel and iron producing company, a holding of several steel works in southern Germany. Created after the Anschluss of Austria, it formed the part of the so-called Reichswerke Hermann Göring AG cartel, the main supplier of steel and iron for the German war industry during World War II. It is also argued that it was the largest steel mill complex in Europe at that time.