The 1951 Formula One season was the fifth season of FIA Formula One motor racing. It featured the second World Championship of Drivers, which was contested over eight races between 27 May and 28 October 1951. The season also included several non-championship races for Formula One cars.

Juan Manuel Fangio won his first Drivers' Championship, beating reigning champion and Alfa Romeo teammate Nino Farina, as well as several drivers from their main rival, Ferrari. Alfa Romeo has not won any Formula One championship since.

Multiple teams, including Alfa Romeo, were running chassis from before World War II. Regulation changes for 1952, however, would make them obsolete.

The following teams and drivers competed in the 1951 FIA World Championship of Drivers. The list does not include those that only contested the Indianapolis 500.

Ferrari's newer, naturally aspirated 4.5-litre cars offered a real challenge to the Alfas, which were nearing the end of their development potential. The Ferraris were able to capitalize on the inefficiency of the Alfa's very thirsty engines, particularly at Silverstone. Although Alfas won four races, with Fangio taking the championship, Ferrari's three victories spelled the end for the Alfas. BRM made their only championship appearance with the V16 at Silverstone, and the old, slow Talbots were increasingly outclassed.

Points were given to the top 5 finishers (8, 6, 4, 3, 2). One point was given for the fastest lap. Only the best four of eight scores counted towards the world championship. Points for shared drives were divided equally between the drivers, regardless of who had driven more laps.

Although the official championship season would start in late May in Switzerland, a handful of non-championship events were to be run. The first was the first-ever Syracuse Grand Prix near the ancient city of Syracuse on the southern island of Sicily. This race was won by Italian Luigi Villoresi driving the new 4 1/2 litre Ferrari 375 on the 5.5 kilometres (3.4 mi) public road circuit. Villoresi would triumph again two weeks later at Pau in southwest France over homeland hero Louis Rosier and Nino Farina, driving a Maserati for this race. On the same day, Thai driver Birabongse Bhanudej would triumph at the Richmond Trophy race at Goodwood in southern England in his Maserati.

Three weeks after the Goodwood and Pau races, it was the San Remo Grand Prix in western Italy, not far from Monaco. Alberto Ascari made his first appearance of the season and promptly won in a Ferrari 375 on this twisty and demanding 3.4 kilometres (2.1 mi) street circuit, ahead of his countryman Dorino Serafini and Swiss Rudi Fischer, both in Ferraris. A week later was the Bordeaux Grand Prix in western France, and it was won by Rosier in a Talbot, ahead of Fischer and Briton Peter Whitehead in a Ferrari. Besides Farina, this race did not feature any Italians because they were competing in the Mille Miglia.