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.
He was involved in the development of the programming language CPL, whose influence can be traced on to C, and C++.
He was president of the British Computer Society from 1999 to 2000 and chairman of the Computer Conservation Society from 2007 to 2011.