1991 U.S. Pro Indoor – Singles

Pete Sampras was the defending champion.

Ivan Lendl won the title, defeating Sampras, 5–7, 6–4, 6–4, 3–6, 6–3 in the final.

Seeds
• # Ivan Lendl (champion)

• # 🇺🇸 Pete Sampras (final)

• # 🇺🇸 Brad Gilbert (semifinals)

• # 🇺🇸 John McEnroe (semifinals)

• # 🇺🇸 Jay Berger (second round)

• # 🇺🇸 Jim Courier (second round)

• # 🇩🇪 Michael Stich (quarterfinals)

• # 🇺🇸 Tim Mayotte (second round)

• # Petr Korda (quarterfinals)

• # 🇺🇸 Derrick Rostagno (second round)

• # 🇦🇺 Darren Cahill (third round)

• # Mark Koevermans (second round)

• # 🇦🇺 Wally Masur (third round)

• # Paul Haarhuis (third round)

• # Gary Muller (third round)

• # 🇺🇸 Patrick McEnroe (second round)