Diego Marabelli was an Italian professional and independent road cyclist between 1936-47, riding for the Bianchi, Aquilano and Arbos teams. He won the 16th stage of the Giro d’Italia between Recoaro Terme and Bergamo in 1938, and also won stages in the 1939 Pescara - Senigallia, and the 1940 Genova - Pisa races. Marabelli won the 1942 Milano-Modena road race when he was riding for the Dopolavoro Safar team. His best overall finish in the Giro was 11th in 1938 and he was also classified 15th on three occasions between 1939-46. Beaten in the sprint by Gino Bartali to finish second in the 1936 Giro di Lombardia, Marabelli was beaten by Olimpio Bizzi in the Tre Valli Varesine the following year. Marabelli took part in the Milano - Sanremo six times, obtaining his best result of 13th in 1937.