| Type: | EC |
| Grand Prix: | Italian |
| Date: | 24 May |
| Year: | 1931 |
| Official Name: | IX Gran Premio d'Italia |
| Country: | Italy |
| Flag Suffix: | 1861 |
| Race No: | 1 |
| Season No: | 3 |
| Location: | Autodromo Nazionale di Monza Monza, Italy |
| Course Mi: | 6.21 |
| Course Km: | 10.00 |
| Distance Laps: | 155 |
| Distance Mi: | 963.14 |
| Distance Km: | 1550.03 |
| Pole Driver: | Robert Sénéchal |
| Pole Team: | Delage |
| Pole Country: | France |
| Pole Driver2: | Henri Frètet |
| Pole Country2: | France |
| Grid From Ballot: | True |
| Fast Driver: | Giuseppe Campari |
| Fast Team: | Alfa Romeo |
| Fast Time: | 3:32.8 |
| Fast Country: | Italy |
| Fast Flag Suffix: | 1861 |
| First Driver: | Giuseppe Campari |
| First Team: | Alfa Romeo |
| First Country: | Italy |
| First Flag Suffix: | 1861 |
| First Driver2: | Tazio Nuvolari |
| First Country2: | Italy |
| First Flag Suffix2: | 1861 |
| Second Driver: | Ferdinando Minoia |
| Second Team: | Alfa Romeo |
| Second Country: | Italy |
| Second Flag Suffix: | 1861 |
| Second Driver2: | Baconin Borzacchini |
| Second Country2: | Italy |
| Second Flag Suffix2: | 1861 |
| Third Driver: | Albert Divo |
| Third Team: | Bugatti |
| Third Country: | France |
| Third Driver2: | Guy Bouriat |
| Third Country2: | France |
The 1931 Italian Grand Prix was a Grand Prix motor race held at Monza on 24 May 1931. The race was the first of three Grands Prix that were part of the inaugural European Championship. The Alfa Romeo works team pairing of Giuseppe Campari and Tazio Nuvolari won the race, ahead of their teammates Ferdinando Minoia and Baconin Borzacchini in second, while third place went to the works Bugattis of Albert Divo and Guy Bouriat.[1]
— Luigi Arcangeli was originally designated as Campari's co-driver in car #26, but he was replaced by Marinoni after he was killed during practice.[1]
Grid positions were allocated by drawing lots.[1]
| Pos | No | Driver | Car | Laps | Time/Retired | Distance (km) | Grid | Points |
|---|---|---|---|---|---|---|---|---|
| 1 | 26 |  Giuseppe Campari | Alfa Romeo 8C-2300 | 155 | 10:00:0.7 | 1557.754 | 3 | 1 |
| Tazio Nuvolari | n/a | |||||||
| 2 | 30 | Ferdinando Minoia | Alfa Romeo 8C-2300 | 153 | +2 laps | 1535.087 | 4 | 2 |
| Baconin Borzacchini | n/a | |||||||
| 3 | 14 |  Albert Divo | Bugatti T51 | 152 | +3 laps | 1525.319 | 9 | 3 |
| Guy Bouriat | 3 | |||||||
| 4 | 18 | Jean-Pierre Wimille | Bugatti T51 | 138 | +17 laps | 1386.082 | 2 | 4 |
| Jean Gaupillat | 4 | |||||||
| 5 | 22 |  Boris Ivanowski | Mercedes-Benz SSK | 134 | +21 laps | 1343.255 | 6 | 4 |
| Henri Stoffel | 4 | |||||||
| 6 | 32 | Francesco Pirola | Alfa Romeo 6C-1500 | 129 | +26 laps | 1290.243 | 14 | 4 |
| Giovanni Lurani | 4 | |||||||
| 7 | 38 | Amedeo Ruggeri | Talbot 700 | 129 | +26 laps | 1290.000 | 12 | 4 |
| Renato Balestrero | 4 | |||||||
| 8 | 8 | Umberto Klinger | Maserati 26M | 114 | +41 laps | 1140.000 | 13 | 5 |
| Pietro Ghersi | 5 | |||||||
| Ret | 40 | Carlo di Vecchio | Talbot 700 | 87 | +68 laps | 870.000 | 8 | 5 |
| Gerolamo Ferrari | 5 | |||||||
| NC | 20 | Robert Sénéchal | Delage 15S8 | 81 | +74 Laps | 809.977 | 1 | 5 |
| Henri Frètet | 5 | |||||||
| Ret | 16 | Marcel Lehoux | Bugatti T51 | 49 | Con-rod | 490.000 | 5 | 6 |
| Philippe Étancelin | 6 | |||||||
| Ret | 12 | Achille Varzi | Bugatti T51 | 44 | Differential | 440.000 | 11 | 6 |
 Louis Chiron | 6 | |||||||
| Ret | 28 | Tazio Nuvolari | Alfa Romeo Type A | 31 | Mechanical | 310.000 | 7 | 7 |
| Baconin Borzacchini | 7 | |||||||
| Ret | 50 | Alfredo Caniato | Alfa Romeo 6C 1750 | 14 | 140.000 | 10 | 7 | |
| Mario Tadini | 7 | |||||||
| DNS | 24 | Antonio Maino | Mercedes-Benz SSK | Did not start | 8 | |||
| Gildo Strazza | 8 | |||||||
| DNS | 36 | Luigi Castelbarco | Maserati 26M | Did not start | 8 | |||
| Tino Bianchi | 8 | |||||||
| Sources: | ||||||||
— Nuvolari and Borzacchini did not receive the points for first and second place, respectively, because they were not driving in their designated cars. The seven points apiece that they received were for driving car #28, which completed less than a quarter of the race distance. Attilio Marinoni and Goffredo Zehender, who had been designated to drive cars #26 and #30, respectively, both received eight points, since they did not take part in the race.[1]
— Ruggeri and Balestrero were initially credited with 1290.534 km, putting them in sixth place. However, their final lap took more than five minutes to complete, so the fraction of the lap completed prior to the ten-hour mark was eliminated, demoting the pair to seventh, and promoting Pirola and Lurani to sixth.[1]
— Sénéchal and Frètet were not classified because they failed to complete at least three-fifths of the number of laps achieved by the race winner.[1]
Notes:
Carlo Pedrazzini