Ioannis Kontoyiannis (born January 1972) is a Greek mathematician and information theorist. He is the Churchill Professor of Mathematics for Operational Research with the Statistical Laboratory, in the Department of Pure Mathematics and Mathematical Statistics, of the University of Cambridge. He is also a Fellow of Darwin College, Cambridge, an affiliated member of the Division of Information Engineering, Cambridge, a Research Fellow of the Foundation for Research and Technology - Hellas, a Senior Member of Robinson College, Cambridge, and a trustee of the Rollo Davidson Trust.