The 1991 Portuguese Grand Prix was a Formula One motor race held at the Autódromo do Estoril on 22 September 1991. It was the thirteenth race of the 1991 Formula One World Championship. The 71-lap race was won by Italian driver Riccardo Patrese, driving a Williams-Renault, after he started from pole position. Patrese's teammate and Drivers' Championship challenger, Briton Nigel Mansell, led until a pit stop went wrong, resulting in his disqualification from the race. Brazilian Ayrton Senna finished second in a McLaren-Honda, thus increasing his lead over Mansell in the championship to 24 points with three races remaining, with Frenchman Jean Alesi finishing third in a Ferrari. Pre-race The only change to the driver line-up was that Johnny Herbert was back at Lotus, replacing Michael Bartels, who had failed to qualify in his three outings for the team. Qualifying Pre-qualifying report It was the fourth consecutive 1–2 for the Brabham team in Friday morning pre-qualifying, with Martin Brundle outpacing his team-mate Mark Blundell by just 0.049 of a second. Third was Gabriele Tarquini in the AGS, just under three tenths of a second off the pace in the new JH27. The Footwork of Michele Alboreto was fourth, the Italian's fourth pre-qualifying success in five attempts. The four drivers to miss out included Tarquini's team-mate Fabrizio Barbazza in fifth position, although he was closer to the pace than in previous events, driving the new AGS JH27 for the first time. Olivier Grouillard could only manage sixth place on this occasion for Fondmetal, his eighth pre-qualifying failure this season, and the Frenchman was sacked by the team after the Grand Prix weekend. Alex Caffi struggled again in the other Footwork in seventh place, his fourth failure in five pre-qualifying attempts, in contrast with his team-mate Alboreto. At the bottom of the time sheets, Pedro Chaves was unable to post a representative time at his home event in the Coloni, but the team announced it had been purchased by Italian shoe designer Andrea Sassetti. Pre-qualifying classification Qualifying report Qualifying saw the top teams' second drivers beating the championship contenders. Riccardo Patrese took pole ahead of Gerhard Berger, with Ayrton Senna and Nigel Mansell third and fourth respectively. The top ten was rounded out by Alain Prost, Jean Alesi, Maurício Gugelmin, Pierluigi Martini, Ivan Capelli, and Michael Schumacher, the Benetton team a little off their usual pace. Qualifying classification Race Race report On