1991 ATP Championship Series, Single Week

The 1991 ATP Championship Series, Single Week was a series of tennis tournament that was part of the 1991 ATP Tour, the elite tour for professional men's tennis organised by the Association of Tennis Professionals. It formed the tier below the Grand Slam tournaments.

Results
{{Legend|#ddfddd|First-time singles Masters champion.}} {{Legend|#0|text= * |Indicates only one of the two players was a first-time doubles champion.}}