The inaugural Italian Grand Prix took place on 4 September 1921 at a 10.7-mile circuit near Montichiari. The following year the race transferred to Monza, a purpose-built autodrome constructed in just 110 days in the Parco di Monza north of Milan. At the time of its completion in 1922, Monza was only the third permanent autodrome in the world, following Brooklands in England and Indianapolis in the United States. The 10-kilometre circuit combined a banked section with a road course and was immediately very fast.
The race counted toward the World Manufacturers' Championship from 1925 to 1928, and toward the European Championship from 1931 to 1932 and from 1935 to 1938, reflecting its central position in the international calendar throughout the prewar period.
The 1928 race marked the beginning of Monza's long, painful association with tragedy. Italians Emilio Materassi in a Talbot and Giulio Foresti in a Bugatti were fighting hard when Materassi's car touched Foresti's rear wheel at around 200 km/h coming off the banking. Materassi lost control, cleared a wide ditch, and ploughed into an unprotected grandstand opposite the pits, killing himself and 27 spectators and injuring 26 more. It was the worst accident in motor racing history at the time and remained so until the 1955 Le Mans disaster. The Italian Grand Prix went on a three-year hiatus following the catastrophe.
When the race returned, tragedy struck again in 1933. During the Monza Grand Prix held on the same day as the Italian Grand Prix, three leading drivers were killed on what became known as the "Black Day of Monza." Giuseppe Campari and Baconin Borzacchini both died when a patch of oil on the south banking caused separate crashes in quick succession. Later in the day, Polish aristocrat Count Stanislas Czaykowski was killed when his Bugatti's engine failure caused a fire and he flew off the banking at the same spot. Enzo Ferrari, who had been close to both Campari and Borzacchini, was profoundly hardened by the events; racing historians regard the day as the end of the sport's carefree early era.
From 1934, the Italian Grand Prix fell under the shadow of German dominance. Mercedes-Benz and Auto Union, backed by the Nazi state, brought highly developed supercharged cars that outpowered and outclassed the Italian opposition. Circuit modifications also reflected the era: after the disasters on the banking, the race used the Florio circuit configuration from 1934, with various chicane arrangements, before eventually settling back on a modified layout. Rudolf Caracciola won for Mercedes in 1934 and 1937, the latter edition run not at Monza but on a street circuit in Livorno. In 1938, the race returned to Monza and was won by Tazio Nuvolari in a mid-engined Auto Union.
The one towering Italian resistance in this era came from Nuvolari himself, who drove with extraordinary skill and bravado against vastly superior machinery on multiple occasions. His performances made him the Italian public's hero and the embodiment of Latin defiance against Germanic technical superiority.
The Italian Grand Prix was held in 1939 at Monza, where Caracciola took victory for Mercedes in what would be the last running before the Second World War. Renovation work began at Monza immediately after that race, but the outbreak of war in September 1939 meant the circuit would not host a Grand Prix again until 1948 — and even then, the 1947 running was held at a fairgrounds in Milan's Portello district, and the 1948 edition at Valentino Park in Turin, before the race finally returned to Monza in 1949.
The prewar Italian Grand Prix shaped the sport in fundamental ways. Monza's combination of high speed and concentrated drama attracted the best teams and drivers of every generation, and the circuit's dangers forced recurring debates about what standards of safety and circuit design were tolerable. The tragedies of 1928 and 1933 left marks on the sport's culture and on Enzo Ferrari personally, who transformed his experiences at Monza into the steely, win-at-all-costs philosophy that defined Scuderia Ferrari for decades. The race's World Championship participation from 1925 onward, and its European Championship status through the 1930s, cemented its place as one of the truly indispensable events in Grand Prix history.