The 1981 Mercedes Cup, was a men's tennis tournament played on outdoor clay courts and held at the Tennis Club Weissenhof in Stuttgart, West Germany that was part of the 1981 Grand Prix circuit. It was the fourth edition of the tournament and was held from 13 July until 19 July 1981. First-seeded Björn Borg won the singles title.
Björn Borg defeated Ivan Lendl, 1–6, 7–6, 6–2, 6–4
Peter McNamara / Paul McNamee defeated Mark Edmondson / 
Mike Estep, 2–6, 6–4, 7–6