1991 Italian Open – Men's singles

Emilio Sánchez won the men's singles tennis title at the 1991 Italian Open after Alberto Mancini retired from the final, with the scoreline at 6–3, 6–1, 3–0.

Thomas Muster was the defending champion, but lost to Goran Prpić in the third round.

Seeds
• # 🇩🇪 Boris Becker (withdrew)

• # 🇺🇸 Andre Agassi (first round)

• # 🇺🇸 Pete Sampras (second round)

• # Goran Ivanišević (first round)

• # 🇪🇸 Sergi Bruguera (semifinals)

• # 🇺🇸 Jim Courier (third round)

• # 🇸🇪 Jonas Svensson (second round)

• # 🇺🇸 Brad Gilbert (first round)

• # 🇪🇸 Emilio Sánchez (champion)

• # 🇩🇪 Michael Stich (first round)

• # Andrei Cherkasov (quarterfinals)

• # 🇦🇷 Guillermo Pérez Roldán (first round)

• # Jakob Hlasek (second round)

• # 🇸🇪 Magnus Gustafsson (second round)

• # Alexander Volkov (second round)

• # Karel Nováček (first round)