|Date 12 May 1991|
Course length 3.328 km (2.068 mi)
|Course Street circuit|
|Official name XLIX Grand Prix Automobile de Monaco|
Location Circuit de Monaco, Monte Carlo
Distance 78 laps, 259.584 km (161.298 mi)
The 1991 Monaco Grand Prix was a Formula One motor race held at Monaco on 12 May 1991.
Ayrton Senna shocked no-one by taking pole position, but second place was a surprise with Stefano Modena taking full advantage of the superior Pirelli qualifying tyres to be second followed by Patrese, Piquet, a disappointed Mansell, Berger, Prost, Moreno, Alesi, and de Cesaris. Alex Caffi had a huge accident in practice and would not participate in the race. Elsewhere Martin Brundle was disqualified for missing a weight check.
At the start, Senna got away well followed by Modena, Patrese, Mansell, and Prost. In the usual first corner mayhem Berger ran into the back of Piquet, dropping the Austrian to the back of the pack and breaking Piquet's suspension, Berger would later crash out. Senna quickly built up a huge lead over Modena and Patrese, and both the chasers were eliminated on lap 42 when Modena's engine blew in the tunnel spreading oil on the track which caused Patrese to crash. Senna now had a huge lead over Prost and Mansell, but the Englishman was in no mood to stay third and passed Prost with a daring move going into the chicane. Prost would later pit to repair a loose wheel and problems with the stop dropped him down to fifth.
Senna duly won his fourth Monaco Grand Prix in five years by 18 seconds over Mansell, who drove a brilliant race, Alesi, Moreno, Prost, and Emanuelle Pirro in the Dallara. The second-place finish was Nigel Mansell's first points of the season and the gearbox issues that had troubled the start of his season did not re-appear.