1991 Thriftway ATP Championships – Singles

Guy Forget defeated Pete Sampras in the final, 2–6, 7–6(7–4), 6–4 to win the singles tennis title at the 1991 Cincinnati Masters.

Stefan Edberg was the defending champion, but lost to Sampras in the quarterfinals.

Seeds
The top eight seeds received a bye to the second round. • # 🇩🇪 Boris Becker (semifinals)

• # 🇸🇪 Stefan Edberg (quarterfinals)

• # Ivan Lendl (third round)

• # 🇺🇸 Jim Courier (semifinals)

• # 🇺🇸 Andre Agassi (third round)

• # 🇫🇷 Guy Forget (champion)

• # 🇺🇸 Pete Sampras (final)

• # 🇺🇸 David Wheaton (third round)

• # 🇪🇸 Emilio Sánchez (first round)

• # Andrei Cherkasov (quarterfinals)

• # Jakob Hlasek (second round)

• # 🇺🇸 Brad Gilbert (quarterfinals)

• # 🇺🇸 Michael Chang (third round)

• # 🇺🇸 Derrick Rostagno (quarterfinals)

• # 🇺🇸 Richey Reneberg (first round)

• # 🇸🇪 Jonas Svensson (first round)