Prof. Dr. Ernst Willi Messerschmid (born May 21, 1945) is a German physicist and former astronaut. Born in Reutlingen, Germany, Messerschmid finished the Technisches Gymnasium in Stuttgart in 1965. After two years of military service he studied physics at the University of Tübingen and Bonn, receiving diploma degree in 1972 and doctorate in 1976. From 1970 to 1975 he was also visiting scientist at the CERN in Geneva, working on proton beams in accelerators and plasmas. From 1975 to 1976 he worked at the University of Freiburg and the Brookhaven National Laboratory (New York), In 1977, he joined DESY in Hamburg to work on the beam optics of the PETRA storage ring.