The 1991 Belgian Grand Prix was a Formula One motor race held at the Circuit de Spa-Francorchamps on 25 August 1991. It was the eleventh race of the 1991 Formula One World Championship. The 44-lap race was won by Brazilian Ayrton Senna, driving a McLaren-Honda, after he started from pole position. His Austrian teammate Gerhard Berger finished second, with another Brazilian, Nelson Piquet, third in a Benetton-Ford. Senna's Drivers' Championship rival, Briton Nigel Mansell, retired with an electrical failure, allowing Senna to extend his lead over him to 22 points with five races remaining.

The race marked the debut of future seven-time World Champion, German Michael Schumacher, driving a Jordan-Ford. Schumacher qualified seventh, which matched the team's season-best grid position, and Schumacher outqualified veteran Andrea de Cesaris. Although he retired on the opening lap with a clutch failure, Schumacher's debut impressed the paddock. His seventh place qualifying was done in a midfield car, the Jordan 191, which he drove half a day of testing and at a track he had never raced at.

The Jordan team dominated the headlines leading up to the Belgian Grand Prix. Driver Bertrand Gachot was serving an eighteen-month prison sentence in an English jail (from which he would ultimately be released after just two months) as a result of an altercation with a London taxi driver, so the team had decided to replace him with young German driver Michael Schumacher. Elsewhere, Johnny Herbert had returned to Lotus after having missed the previous two races due to Formula 3000 commitments in Japan.

As at the previous event in Hungary, the Friday morning pre-qualifying session was dominated by Brabham, who achieved their second 1–2 in succession. On this occasion, Martin Brundle was fastest, 1.5 seconds quicker than his team-mate Mark Blundell. Third, over 3.5 seconds slower than Brundle, was Olivier Grouillard for Fondmetal, the fourth time this season he had pre-qualified. Over a second behind Grouillard was Alex Caffi, pre-qualifying for the first time in three attempts for Footwork.

Missing out by 0.45 of a second in fifth place was Caffi's team-mate Michele Alboreto, the first time he had failed to pre-qualify in his three attempts. A fraction slower in sixth, after suffering a huge accident, was Gabriele Tarquini in the AGS, nearly two seconds ahead of Pedro Chaves in the Coloni. Bottom of the time sheets was the other AGS of Fabrizio Barbazza, who also crashed during the session.

Ayrton Senna was fastest most of the weekend and duly took pole position, but Ferrari were right on his heels. Alain Prost qualified third on the road while Jean Alesi had set the fastest first and second sectors only to come across traffic at the end of the lap, resulting in a sixth place start, which would be elevated to fifth. Riccardo Patrese had originally qualified second, but after Saturday qualifying his car was found to not have a reverse gear as per the safety regulations and Patrese's Saturday times were wiped out, he had to start a disappointing seventeenth on the grid. Patrese's misfortune promoted Prost to second, with Nigel Mansell third, Gerhard Berger fourth, Alesi fifth, and Nelson Piquet sixth while the sensation of qualifying, Schumacher, was an amazing seventh for his first Grand Prix. The top ten was completed by Roberto Moreno in the second Benetton, Pierluigi Martini in a Minardi and the ever-impressive Stefano Modena in a Tyrrell.

At the start both Senna and Prost got away well and the Brazilian led into the first corner. Mansell was third followed by Berger, Piquet, and Schumacher. The German's luck however would run dry just after Eau Rouge when his clutch failed. Out at the front Senna continued to lead but Prost's day ended on lap three when his Ferrari caught on fire, leaving Mansell in second. The determined Englishman proceeded to go after Senna and the two battled lap after lap until Senna pitted for new tyres on lap 15. The stop was a bad one and when Mansell pitted two laps later he was able to emerge ahead of Senna, but just behind Berger who had yet to stop. These stops left Piquet in the lead for one lap before he made his stop.

Mansell quickly closed in on Berger and managed to sweep past into Les Fagnes. When Berger stopped a lap later he had problems and then spun on the pit exit and came back right in front of Modena, nearly causing a bad accident. Mansell's big lead would not last, however as on lap 22 his car stopped, having succumbed to electronic problems, his championship hopes taking a major hit.