The 1991 IBM ATP Tour was the elite tour for professional men's tennis organized by the ATP Tour.

The IBM ATP Tour included the Grand Slam tournaments (organized by the International Tennis Federation (ITF)), the ATP Championship Series, Single-Week, the ATP Championship Series, the ATP World Series and the ATP Tour World Championships.

The World Team Cup, Davis Cup (organized by the ITF) and Grand Slam Cup (organized by the ITF) are included in this calendar but did not count towards the Tour.

This is the complete schedule of events on the 1991 IBM ATP Tour, with player progression documented from the quarterfinals stage.

List of players and singles titles won, alphabetically by last name: The following players won their first title: