See main article: 2003 Italian Open (tennis).
Félix Mantilla defeated Roger Federer in the final, 7 - 5, 6 - 2, 7 - 6(10 - 8) to win the men's singles tennis title at the 2003 Italian Open.
Andre Agassi was the defending champion, but lost in the first round to David Ferrer.
A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated.