1991 ATP Tour World Championships – Singles

Pete Sampras defeated Jim Courier in the final, 3–6, 7–6(7–5), 6–3, 6–4 to win the singles title at the 1991 ATP Tour World Championships. It was his first Tour Finals title.

Andre Agassi was the defending champion, but was defeated by Courier in the semifinals.

Ilie Năstase group
''Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-players-ties, head-to-head records; 4. in three-players-ties, percentage of sets won, or of games won; 5. steering-committee decision.''

John Newcombe group
''Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-players-ties, head-to-head records; 4. in three-players-ties, percentage of sets won, or of games won; 5. steering-committee decision.''