The San Marino Grand Prix (Italian: Gran Premio di San Marino) was a Formula One championship race which was run at the Autodromo Internazionale Enzo e Dino Ferrari in the town of Imola, near the Apennine mountains in Italy, between 1981 and 2006. It was named after nearby San Marino as there already was an Italian Grand Prix held at Monza even though the Imola Circuit was in Italy and not within San Marino's own territory. In 1980, when Monza was under refurbishment, the Imola track was used for the 51st Italian Grand Prix.

The area around Imola is home to several racing car manufacturers – namely Ferrari, Lamborghini, Maserati, Racing Bulls (RB) (formerly known as Minardi, Toro Rosso and AlphaTauri), Dallara and Stanguellini. Following the Second World War, the town launched a program to try to improve the local economy. Four local motor racing enthusiasts proposed the construction of a new road linking existing public roads, which was used by the local car manufacturers to test their prototypes. Construction began in March 1950. The first test run took place two years later when Enzo Ferrari sent a car to the track and Alberto Ascari ran some demonstration laps.

In April 1953, the first motorcycle races took place at Imola, and the first car race took place in June 1954. In April 1963, the first race with Formula One cars took place at Imola, as a non-championship event, won by Jim Clark for Lotus. A further non-championship event took place at Imola in 1979, which was won by Niki Lauda for Brabham-Alfa Romeo.

In 1980, the Italian Grand Prix moved from the high-speed Monza circuit to Imola (later known as Autodromo Dino Ferrari), as a direct result of 1978's startline pile-up, which claimed the life of the popular Swedish driver Ronnie Peterson. It was won by Nelson Piquet for Brabham-Ford. The following year, the Italian Grand Prix returned to Monza. This left the owners of the Imola circuit without a Grand Prix. They were eager to remain on the calendar, however, and with an Italian Grand Prix already on the calendar, they asked the Automobile Club of San Marino, the motorsport authority of the nearby Republic of San Marino, to apply for their own Grand Prix. Their application was successful and the San Marino Grand Prix was born.

The 1981 event saw Canadian Gilles Villeneuve qualify his Ferrari on pole position. He led the race for the first 19 laps until he pitted for fresh tyres. His teammate Didier Pironi inherited the lead but was eventually caught by Nelson Piquet, who eventually won the race with Riccardo Patrese taking second and Carlos Reutemann coming home third. 1982 saw another memorable race; it was boycotted by most of the FOCA teams and was a turning point in Formula One's history. Only 14 cars competed, and after the Renaults of Alain Prost and René Arnoux retired, Ferrari had no competition, and finished first and second. However, Ferrari's triumph was not so clean-cut. Teammates Villeneuve and Pironi battled fiercely on the track, but while the third-placed Tyrrell of Michele Alboreto was far behind, Ferrari ordered their drivers to slow down to minimize the risk of mechanical failure or running out of fuel. Villeneuve believed this order also meant that the cars were to maintain position on the track. However, Pironi believed that the cars were free to race, and passed Villeneuve. Villeneuve believed that Pironi was simply trying to spice up an otherwise dull race, and duly re-passed his teammate, assuming that he would then hold station for the remainder of the race. Thus, Villeneuve failed to protect the inside line going into the Tosa corner on the final lap, and Pironi passed him to take the win. Villeneuve was irate at what he saw as Pironi's betrayal, although opinion inside the Ferrari team was split over the true meaning of the order to slow down. Villeneuve's expression was sullen on the podium, enraged by Pironi's actions. He was quoted afterwards as saying, "I'll never speak to Pironi again in my life." They proved to be prophetic words, as he was still not on speaking terms with his teammate when he died during qualifying for the Belgian Grand Prix two weeks later.

1983 saw Ferrari win again, with Patrick Tambay taking top honors and Riccardo Patrese crashing his Brabham hard at Acquaminerale while battling with Tambay for the lead. 1984 saw Prost win in a McLaren, and 1985 was yet another exciting race. Brazilian Ayrton Senna led much of the race; but Ferrari driver Stefan Johansson had started in 15th place, and was quickly making up places in only his second drive for the Prancing Horse; he passed Senna at the end of Lap 61 and took the lead. Unfortunately, Johansson had a fuel problem and retired; many others subsequently began to run out of fuel and Prost finished 1st only to be disqualified later when his car was weighed in as 2 kg underweight; victory was then handed to 2nd-placed Italian Elio de Angelis. 1986 saw Prost win yet again in a fuel-starved race. 1987 saw Senna take pole position narrowly from Briton Nigel Mansell; his teammate Nelson Piquet had a huge crash at Tamburello, and although he only received minor injuries, he did not participate in the race due to FIA doctor Sid Watkins declaring the Brazilian unfit for racing. 1988 saw the McLaren duo of Prost and Senna totally dominate; they were both three seconds faster in qualifying than the next-fastest qualifier Piquet in a Lotus.

1989 saw the circuit renamed as Autodromo Enzo e Dino Ferrari to honor the memory of Enzo Ferrari, who had died the year before. It was another notable event which saw Austrian Gerhard Berger crash heavily while going straight on at Tamburello; he was knocked unconscious and the car, after coming to rest and being soaked with fuel, burst into flames. The Austrian survived this crash, and only received burns to his hands and missed the next race, the Monaco Grand Prix. The race was red-flagged and restarted, generating one of the most famous and acrimonious rivalries in sports history. McLaren teammates Prost and Senna made an agreement that whoever got to the slow, long Tosa corner first would stay in front. But as the two teammates started, Prost got the better start and led going into Tamburello. However, Senna got alongside Prost going through the flat-out Villeneuve right-hander and passed the Frenchman into Tosa. Prost was furious, as he saw this as a broken agreement. He followed and attempted to pass Senna on many occasions, eventually going off at the Variante Bassa chicane. Senna won the race, Prost finished second.

In 1990 pole-sitter Senna suffered a puncture on the third lap; leaving Nigel Mansell and Berger to battle hard for the lead. Mansell did a full 360 degree spin on the straight between Tamburello and Villeneuve after Berger forced the Englishman onto the grass; Mansell kept the Ferrari on the road; but because of this spin the V12 engine got grass in it and failed soon after. Riccardo Patrese won the race in a Williams, followed by Berger, who had wrecked his tyres and couldn't keep Patrese from passing him. The 1991 was a rain-soaked event, and Prost spun off on the grass at Rivazza on the parade lap, stalling the engine. Gerhard Berger did the same, but he kept his McLaren going; McLaren finished first and second, with Senna in front of Berger, with Finnish new-boys JJ Lehto finishing on the podium and Mika Häkkinen finishing fifth. 1992 saw the Williams pair of Nigel Mansell and Patrese dominate, and 1993 saw Prost win, now driving a Williams.