Alexander D. MacKerell, Jr. is an American biophysicist who is the Grollman-Glick Professor of Pharmaceutical Sciences at the University of Maryland, Baltimore (UMB) and the Director of the Computer-Aided Drug Design (CADD) Center at UMB. He is also the Co-Founder and Chief Scientific Officer of the drug design tech company SilcsBio. In 2022, MacKerell was awarded the prestigious American Chemical Society Award for Computers in Chemical and Pharmaceutical Research.