1991 ATP German Open

1991 ATP German Open
Date6–13 May
Edition85th
CategoryATP Championship Series
Draw56S / 28D
Prize money$750,000
SurfaceClay / outdoor
LocationHamburg, Germany
VenueRothenbaum Tennis Center
Champions
Singles
Karel Nováček
Doubles
Sergio Casal / Emilio Sánchez

The 1991 German Open was a men's tennis tournament played on outdoor clay courts. It was the 85th edition of the Hamburg Masters (Hamburg Masters), and was part of the Championship Series category of the 1991 ATP Tour. It took place at the Rothenbaum Tennis Center in Hamburg, Germany, from 6 May until 13 May 1991. Karel Nováček, who was seeded 13th, won the singles title.