Ernst Willi Messerschmid (born 21 May 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 a Diplom degree in 1972 and doctorate in 1976.

From 1970 to 1975 he was also a visiting scientist at the CERN in Geneva, working on proton beams in accelerators and plasmas.

In January 2005, he returned to the University of Stuttgart teaching on subjects of Astronautics and Space Stations.