David Fielding Hartley FBCS (born 14 September 1937) is a computer scientist and Fellow of Clare College, Cambridge. He was Director of the University of Cambridge Computing Service from 1970–1994, Chief Executive of United Kingdom Joint Academic Network (JANET) 1994–1997, and Executive Director of Cambridge Crystallographic Data Centre (CCDC) 1997–2002. He is now much involved with the National Museum of Computing.