The final race of the 1951 Formula 1 season will take place at the Pedralbes Circuit in Barcelona, Spain. The circuit has previously been used for the non-championship Penya Rhin Grand Prix in 1946, 1948 and 1950. Luigi Villoresi won the 1948 race whilst the previous year, Alberto Ascari started the Ferrari 375’s success with a win at the event. The success of the previous years’ Penya Rhin Grand Prix impressed the CSI enough to allow it to host the Spanish Grand Prix for the 1951 World Championship. A year after the debut of the Ferrari 375, Alberto Ascari is hoping to take his first world championship in the 1951 finale. However, he still sits two points behind Juan Manuel Fangio's 27 points. Fangio, for the second year in a row, is in for a chance at the world title at the last race. He lost the 1950 title to his teammate, Giuseppe Farina, due to poor reliability throughout the season, however now, in 1951, Fangio is determined not to let the title slip through his fingers. For the season's last race, Alfa Romeo arrives in Spain with its traditional line-up of Juan Manuel Fangio, Giuseppe Farina, Felice Bonetto and Emmanuel de Graffenried. Ferrari too will field their usual line-up of Alberto Ascari, José Froilán González, Luigi Villoresi and Piero Taruffi. Peter Whitehead planned to enter his old Ferrari 125 as usual, however he withdrew from the event. The B.R.M. team planned to race with an only car for Reg Parnell; however, following their disastrous reliability at Monza which had prevented their cars from even starting, the team chose to withdraw from the event. Simca-Gordini, the lead constructor of the midfield, will be seen back in action, with the usual line-up of Robert Manzon, Maurice Trintignant and André Simon driving their cars. Amongst the Talbot-Lago privateers, Louis Rosier and Louis Chiron are once again participating for Ecurie Rosier. The other regular privateers for the French constructor include Yves Giraud-Cabantous, Philippe Étancelin, Johnny Claes and Georges Grignard.
Scuderia Milano is due to return with its modified Maserati's, the team employing two Spanish racers to keep the local crowd entertained, Francisco Godia-Salesand and Juan Jover Sañés would be the Spanish representation on the field. Both drivers will be starting their first Grand Prix. Antonio Branca and Chico Landi were both due to enter as Maserati privateers, however they both withdrew their entry. In the last race of the season, Prince Bira of Siam will finally make his first world championship appearance of the season. After a failed first appearance for OSCA with Franco Rol in Monza, Prince Bira decided to enter the OSCA-engined Maserati for the team for the final race of the season. All the paddock's eyes are laid on the progress of Fangio and Ascari, the two championship rivals. Ascari has the advantage of having competed and won here the previous season whilst Fangio never attended the circuit before. Ascari is consistently the quickest throughout practice, the Ferrari driver taking pole position ahead of the race. Fangio is feeling concerned, he was second on the grid but two seconds behind Ascari's pole time. In third, the second Ferrari of González sits a further two seconds from Fangio. Farina is eight tenths behind González's best time. Villoresi's Ferrari stays ahead of the Alfa Romeo of De Graffenried whilst the final works Ferrari's and Alfa Romeo's of Taruffi and Bonetto are seventh and eighth. Bonetto struggled all throughout the session and is only two seconds faster than the Simca-Gordini's that leads the midfield, Manzon sitting ahead of teammates Simon and Trintignant on the grid. Most of the Talbot-Lago contingent follows behind the Simca-Gordini's: Chiron leads Étancelin, Giraud-Cabantous, Claes and Grignard on the grid. Rosier sits twentieth and last on the grid due to consistent mechanical troubles throughout practice. The two local heroes of Francisco Godia-Sales and Juan Jover Sañés qualified eighteenth and nineteenth, Bira simply shows the failure of the Maserati-OSCA hybrid, his car only nineteenth on the grid, ahead of only the troubled Rosier.
An expectant crowd of 250,000 spectators gathers on race day for the exciting finale of the 1951 Formula 1 season. The big battle of the day is once again between Alfa Romeo and Ferrari, and most importantly, Juan Manuel Fangio and Alberto Ascari for the world championship. It’s a disappointment to see one of the home favourites, Juan Jover Sañés, retire his Maserati before the start. The car encountered consistent engine troubles which now forced the Spaniard to withdraw. Only 19 cars are therefore taking the start due to the pre-race retirement of Sañés. The race starts well for Ferrari, Ascari immediately takes the lead whilst González manages to move into second place. Fangio has a poor start and drops down to fourth, his teammate Farina also making it past him on the starting line. However later on the race begins to return in Fangio’s favour: on the second lap González spins, dropping behind Farina, Fangio, Bonetto and Villoresi. On the third lap, Fangio moves past his teammate Farina whilst on the fourth race leader Ascari is overtaken by Fangio's Alfa Romeo. However, this was not completely out of plan for Ferrari. The Ferrari 375 with its better fuel economy is expecting to go the whole race without stopping. The Alfa Romeo's, instead, are expected to make a pit-stop during the race. Despite this, Ferrari begins to fall off the pace. Before the race, the team fitted new smaller diameter wheels. However, the tyres on these smaller wheels struggle to cope with the heavy loading that’s being presented on the Pedralbes Circuit. The Ferraris begin to encounter severe tyre degradation, all their cars are required to make a pit-stop. Taruffi pits on lap 6, Villoresi on lap 8, Ascari on lap 9 and González on lap 14.
There have been a few early retirements, Prince Bira's lone championship appearance in the season lasted a single lap before his Maserati-OSCA broke down. Chiron also retired with ignition troubles whilst Giraud-Cabantous also went out following an accident which saw him hit a stray dog. Grignard would then go out of the race on lap 23 with engine trouble. At the front, Alfa Romeo are now well in control of the race with their four cars occupying the top four following the Ferrari pit-stops. Despite his mishaps, Ascari is determined to take the championship, he quickly makes his way past De Graffenried and Bonetto to move into third place. However, whilst chasing Fangio and Farina, Ascari slides off the circuit and into the sand. The car is undamaged, however a quick precautionary pit-stop sees him drop back behind Bonetto, De Graffenried, González and Villoresi. De Graffenried will not maintain his position for long: steam begins to pour from his bonnet prompting a pit-stop. The Alfa Romeo has its water refuelled and rejoins the race in eighth place. The lead of the midfield is still contested between Manzon, Trintignant and Simon for ninth place. The three Simca-Gordinis are battling hard, however both Simon and Trintignant will soon retire with engine troubles. Manzon too will encounter engine troubles, while the lone Simca-Gordini was determined to make it to the end. Following the troubles of Ascari, González took up the Ferrari charge, his car moving past Bonetto to get in third. However, the two leading Alfa Romeo's of Fangio and Farina, seem to be in continued control of the race. On lap 29, Fangio comes into the pits for his scheduled pit-stop for fuel.
He rejoins the race in second, still ahead of González and remains in prime position to take the world title. Taruffi is having a terrible race for Ferrari, he’s struggling in only eighth position and then, on lap 30, his wheel detaches from the car forcing him to retire from the race. Claes is the next driver to retire on lap 37: his car crashes against some straw barrels lining the circuit, forcing him to pull into the pits to retire. The Ferrari's continue to encounter difficulties, Villoresi is driving slowly with an engine misfire whilst Ascari is forced to make a second pit-stop due to tyre troubles. His championship hopes are constantly slipping away as his rival, Fangio, continues to dominate apparently without problem. González, anyway, is still charging and manages to move past Farina into second place at the following round of Alfa Romeo pit stops. There is little to no consolation for Ferrari: Fangio is dominating, also setting a new lap record for the circuit and will go on to win his third championship win of the season and his first world title, 54 seconds ahead of González. Farina, handing over the title of reigning world champion to Fangio, is still in third place, the only unlapped racer remaining. Ascari fights his way up to fourth position, however it is not enough to be crowned world champion after a dismal race. Bonetto rounds out the top five ahead of De Graffenried who battled water cooling problems throughout the race. Rosier, who started last on the grid, fights his way back up to seventh place in the race. Étancelin finishes eighth ahead of Manzon, who remarkably makes it to the finish line despite his engine problems. In last place, comes the lone Maserati of Godia-Sales. The sole Spaniard was determined to see the finish of the race, his car needing multiple pit-stops for repairs putting him ten laps behind the leaders.