Alastair Harvey MacLennan, AO, MB ChB, MD, FRCOG, FRANZCOG (born 28 March 1945) is a Scottish-Australian physician, professor of obstetrics and gynaecology, medical researcher, and a community health advocate. He studied and practised medicine in Glasgow, Chicago, and Oxford before moving to Australia in 1977 to take up a position at the University of Adelaide, where he went on to become the Professor and Head of the Discipline of Obstetrics and Gynaecology in 2006. He retired from his full-time academic position in 2013, and he is now Emeritus Professor of Medicine. He leads research projects at the Robinson Research Institute, and he is Head of the university's Cerebral Palsy Research Group.