The Carro Armato M11/39 was the first of Italy's medium tank designs although at just 11 tonnes, would barely be considered a light tank in most other armies. Like the CV 33 tankette that it was designed to replace, the M11/39 was armed with twin Breda 8-mm machine guns in the one-man turret. However, a 37-mm gun was added to the right side of the hull; a configuration similar to that of the French Char B1 and the US M3. Despite its limited traverse, it offered considerably superior firepower compared to all previous Italian tank designs. The M11/39 was built with a riveted hull and turret and armor protection was limited to a 30 mm maximum; not enough to provide adequate protection even against the relatively lightly armed British tanks of 1940-41. It was eventually realized that the gun configuration had to be reversed and armor protection increased. This resulted in a successor, the M13/40 which went on to be the most widely used Italian tank of the war. Still, M11/39s were in service in the Balkans, East Africa and North Africa before being gradually replaced.

Design of the M11/39 began in 1936 and the first prototype was ready the following year. No variants aside from the basic tank version were built as production soon shifted to the improved M13/40.