Born in Buddusò, Sardinia, into a working class family, Biondetti began racing motorcycles in 1923 but in 1927 turned to automobiles. By 1931 his performance earned him a spot in Grand Prix motor racing with the Maserati factory team. In 1934, he raced a private Maserati T26M. He sat out 1935 as his international license hadn't been renewed, probably due to political reasons. He continued as privateer in 1936, raced Alfas for Ferrari in 1937 and then as works driver for Alfa Corse during the 1938-40 era. By the time he was able to resume racing after the war, he was already 49 years old. Nevertheless, he dominated Italian endurance racing, driving to victory in the Mille Miglia for three straight years from 1947 through 1949 and the Targa Florio in 1948 and 1949. Clemente Biondetti participated in one Formula one World Championship event, the 1950 Italian Grand Prix. Driving a self-built Ferrari-Jaguar hybrid car, engine problems forced him out of the race thus he failed to score any championship points. Biondetti had for a long time been suffering from cancer and he decided to retire from racing in 1954. He died in Florence early the following year at 57 years old.