See main article: 2004 Ladies German Open.
Amélie Mauresmo won the singles tennis title at the 2004 WTA German Open by walkover, as her opponent Venus Williams withdrew due to a left ankle strain. It was the first title of the year for Mauresmo, and the 11th title of her career.
Justine Henin-Hardenne was the two-time reigning champion, but did not compete this year due to a cytomegalovirus.
The first eight seeds received a bye into the second round.