Joseph Daniel Harris (born August 17, 1951), known nearly universally as Joe Harris, is a mathematician at Harvard University working in the field of algebraic geometry. He attended college at and received his Ph.D. from Harvard in 1978 under Phillip Griffiths.During the 1980s he was on the faculty of Brown University, moving to Harvard around 1988. He served as chair of the department at Harvard from 2002 to 2005.