The Stuttgart Open (currently sponsored by Mercedes and called the Mercedes Cup) is an ATP World Tour 250 series tennis tournament on the ATP Tour. Between 1970 and 1989, the Stuttgart Open was a Grand Prix tennis circuit event. From 1990 to 1999, the Stuttgart Open was an ATP Championship Series tournament. The Championship Series name was changed to ATP International Series Gold in 2000, and the Stuttgart Open was a part of this series from 2000–2001 and 2003–2008. In 2002, the Stuttgart Open was briefly demoted for one year to ATP International Series status. In 2009, the Stuttgart Open was demoted again to the newly named ATP World Tour 250 series status, which it has retained ever since.
Held since 1916 in Stuttgart, Germany, the Stuttgart Open was played on clay up to and including 2014. In 2015, the tournament will be played on grass. Along with the move to grass-courts, the tournament will be staged in the week after the French Open finishes.
Thomas Muster of Austria won the title twice in consecutive years (1995 and 1996).