John Andrew Todd FMedSci FRS (born 23 June 1958) is Professor of Precision Medicine at the University of Oxford, director of the Wellcome Center for Human Genetics and the JDRF/Wellcome Trust Diabetes and Inflammation Laboratory, in addition to Jeffrey Cheah Fellow in Medicine at Brasenose College. He works in collaboration with David Clayton and Linda Wicker to examine the molecular basis of type 1 diabetes.