The 1990–91 Campionato Sammarinese di Calcio season was the 6th season since its establishment. It was contested by 10 teams, and S.C. Faetano won the championship.
Regular season
Results
Championship playoff
First round S.C. Faetano 3-0 S.S. Folgore/Falciano S.S. Juvenes 4-2 S.S. Montevito
Second round S.S. Folgore/Falciano 0-1 S.S. Montevito S.C. Faetano 2-1 S.S. Juvenes
Third round S.S. Juvenes 2-1 S.S. Montevito S.P. Tre Fiori 4-1 S.C. Faetano
Semifinal S.C. Faetano 3-1 S.S. Juvenes
Final S.C. Faetano 1-0 S.P. Tre Fiori
References San Marino - List of final tables (RSSSF)