Michael Herbert Day (March 8, 1927 – June 1, 2018) was a British anatomist and paleoanthropologist. His research concentrated on the morphology of postcranial remains to understand the evolution of locomotion in the hominin clade. He was the author of the Guide to Fossil Man, the first English publication to review the hominin fossil record. Day eventually worked in the Department of Anatomy at the Middlesex Hospital Medical School and served as the Chair of Anatomy at St. Thomas's Hospital Medical School until his retirement.[1]