David John Cameron MacKay, FRS, (born April 22, 1967) is the professor of natural philosophy in the department of Physics at the University of Cambridge.

He was born the fifth child of Donald MacCrimmon MacKay and Valerie MacKay. He was educated at Newcastle High School (later Newcastle-under-Lyme School) and represented Britain in the International Physics Olympiad in Yugoslavia in 1985, receiving the first prize for experimental work. MacKay went up to Trinity College, Cambridge and received a BA in Natural Sciences (Experimental and Theoretical Physics) in 1988. He went to the California Institute of Technology (Caltech) as a Fulbright Scholar. His supervisor in the graduate programme in Computation and Neural Systems was John Joseph Hopfield. He was awarded a PhD in 1992.

In January 1992 MacKay was made the Royal Society Smithson Research Fellow at Darwin College, Cambridge, continuing his cross-disciplinary research in the Cavendish Laboratory, the Department of Physics of the University of Cambridge. In 1995 he was made a University Lecturer in the Cavendish Laboratory. He was promoted in 1999 to a Readership and in 2003 to a Professorship in Natural Philosophy. He was elected a Fellow of the Royal Society in May 2009.