1991 ATP Championship Series, Single Week Singles Singles

| Tournament | Surface | Week | Winner_and_score | Finalist | Semifinalists |
|---|---|---|---|---|---|
| Indian Wells | Hard | March 4 | Jim Courier (16) 4–6, 6–3, 4–6, 6–3, 7–6(4) | Guy Forget (3) | Stefan Edberg (1) Michael Stich (11) |
| Key Biscane | Hard | March 11 | Jim Courier (13) 4–6, 6–3, 6–4 | David Wheaton | Stefan Edberg (1) Richey Reneberg (24) |
| Monte Carlo | Clay | April 22 | Sergi Bruguera 5–7, 6–4, 7–6(6), 7–6(4) | Boris Becker | Horst Skoff Goran Prpić |
| Hamburg | Clay | May 6 | Karel Nováček 6–3, 6–3, 5–7, 0–6, 6–1 | Magnus Gustafsson | Michael Stich Goran Prpić |
| Rome | Clay | May 13 | Emilio Sánchez 6–3, 6–1, 3–0 retired | Alberto Mancini | Goran Prpić Sergi Bruguera |