1991 Campionati Internazionali di San Marino – Singles

Guillermo Pérez Roldán successfully defended his title, by defeating Frédéric Fontang 6–3, 6–1 in the final.

Seeds
• # 🇦🇷 Guillermo Pérez Roldán (champion)

• # 🇪🇸 Jordi Arrese (second round)

• # 🇸🇪 Nicklas Kulti (quarterfinals)

• # 🇦🇷 Franco Davín (quarterfinals)

• # 🇮🇹 Renzo Furlan (semifinals)

• # 🇦🇷 Roberto Azar (semifinals)

• # Nuno Marques (second round)

• # 🇪🇸 José Francisco Altur (first round)