See main article: 2003 Mutua Madrileña Masters Madrid.
Juan Carlos Ferrero defeated Nicolás Massú in the final, 6 - 3, 6 - 4, 6 - 3 to win the singles tennis title at the 2003 Madrid Open.
Andre Agassi was the reigning champion, but did not compete that year.
A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated. All sixteen seeds received a bye into the second round.