1955
For the first time since 1950 Formula 1 returned to the Principality. Mercedes-Benz brought three cars, with Juan-Manuel Fangio and Stirling Moss assigned to the short wheelbase cars and Hans Herrmann his usual car. Hermann crashed during practice and was replaced by Andre Simon. Louis Chiron drove the Lancia and Hawthorn had signed for Vanwall.
Fangio took pole position at Monaco with Ascari next to him and Moss running in the third spot. Eugenio Castellotti's Lancia shared the second row with Jean Behra's Maserati while Roberto Mieres and Luigi Musso were split by Gigi Villoresi's Lancia on row three. Further back Mike Hawthorn made his first appearance in a World Championship event in his Vanwall.
At the start Fangio led at the first corner and was followed by Castellotti, Moss and Ascari. Farina damaged a wheel and stopped to replace it. Castellotti was able to hold off Moss for the first five laps but by then Fangio was too far ahead for Moss to be able to catch him. Ascari made an attempt to pass Castellotti but would end up battling him for a good time. Behra eventually joined in and it was the Frenchman who finally emerged ahead. Castellotti pitted with a flat tire.
The cars of Mercedes-Benz struggled through the Monaco Grand Prix with several problems. Fangio retired with a broken axle and Moss followed with engine trouble. Moss's blown engine allowed Ascari to take the lead. Ascari crashed at the chicane sending him straight into the port of Monaco, through hay bales and sandbags. The crowd had thought the worst but Ascari broke free of his car and swam back up safely. This left Trintignant in the lead and Castellotti in pursuit. Castellotti tried to catch Trintignant but had to be content with second place while Trintignant took the Monaco Grand Prix win. Perdisa took third in Behra's Maserati, the two men having switched cars in mid-race. The remaining Lancias finished fifth and sixth, scoring the teams first points.
Four days following the race Albert Ascari died. He had arrived at Monza to watch Castellotti trying his new Ferrari 750 sports car. Ascari set off to test run the 750 but never came back. The cause of his accident was never determined.
| Pos | No | Driver | Team | Laps | Time/Retired |
| 1 | 44 | Maurice Trintignant | Ferrari | 100 | 2:58:10.2 |
| 2 | 30 | Eugenio Castellotti | Lancia | 100 | 20.2 |
| 3 | 34 | Cesare Perdisa | Maserati | 99 | + 1 Lap |
| 4 | 42 | Nino Farina | Ferrari | 99 | + 1 Lap |
| 5 | 28 | Luigi Villoresi | Lancia | 99 | + 1 lap |
| 6 | 32 | Louis Chiron | Lancia | 95 | + 5 Laps |
| 7 | 10 | Jacques Pollet | Gordini | 91 | + 9 Laps |
| 8 | 48 | Piero Taruffi | Ferrari | 86 | + 14 Laps |
| 9 | 6 | Stirling Moss | Mercedes | 81 | + 19 Laps |
| Ret | 34 | Jean Behra | Maserati | 86 | Spun Off |