Stephen Fleet was educated at Brentwood School, Essex, Lewes County Grammar School, Sussex and St John's College, Cambridge, where he received his doctorate. His research fields were the crystal structure of minerals, particularly phase transformations in minerals and meteorites.
In 1963 Fleet moved to Fitzwilliam House and was a founding fellow when Fitzwilliam achieved collegiate status in 1966. In 1974 he moved to Downing College as bursar and fellow and later served the college as Vice-Master (1985–1987, 1991–1994 and 1997–2000) and as Master from 2000 to 2003. Between 1983 and 1997 Fleet was the University Registrary, the chief administrative officer of the university.
- "Stephen Fleet". The Sunday Times. 5 June 2006.
- Everitt, Barry (31 May 2006). "Stephen Fleet". The Independent.