Sexton, OBE, managed England U21s to two European crowns during the 1980s and was appointed the first technical director at the FA national school at Lilleshall. Sexton played for Luton, West Ham, Leyton Orient, Brighton and Crystal Palace before going into coaching, winning the FA Cup in 1970 with Chelsea and the European Cup Winners' Cup a year later.
FA chairman David Bernstein said: "The whole of The FA is saddened by this news."
He added: "Dave Sexton was synonymous with English coaching and was one of those people that sat right at the heart of our organisation during his time with us.
"He had many friends at the FA including Roy Hodgson and former England managers such as Sven-Goran Eriksson and Terry Venables whom he worked alongside.
"His achievements speak volumes, but his success with the England Under-21 sides of 1982 and 1984 are something that will always be remembered with great fondness.
"Our thoughts are, of course, with Dave's family at this difficult time."
After seven years with Chelsea, Sexton spent four seasons at Old Trafford, where he took United to the 1979 FA Cup final and runners-up spot in the League in 1980.
He also managed QPR and Coventry before taking up the technical director's position at Lilleshall, where he mentored the likes of Glenn Hoddle, Paul Gascoigne, Sol Campbell, Alan Shearer and Michael Owen.
Source: PA
Source: PA