The 1991 BMW Open was a men's tennis tournament held in Munich, Germany and played on outdoor clay courts. The event was part of the ATP World Series category of the Association of Tennis Professionals tour. It was the 75th edition of the tournament and was held from 29 April through 6 May 1991. Unseeded Magnus Gustafsson won the singles title.

Magnus Gustafsson defeated Guillermo Pérez Roldán 3–6, 6–3, 4–3 (Perez-Roldan retired)

Patrick Galbraith / Todd Witsken defeated Anders Järryd / Danie Visser 7–5, 6–4