Alan Mackay-Sim AM (born 16 May 1951) is an Australian biomedical scientist specialising in adult stem cell research, and winner of the 2017 Australian of the Year. Some of his research focuses on olfactory ensheathing cells, which are cells in the human nose that interact with the nervous system to cause a sense of smell. His research into stem cells contributed to the treatment of spinal cord injuries. The restoration of mobility to Darek Fidyka, a Polish paraplegic man, used research by Mackay-Sim.