The 1991 Australian Grand Prix was a Formula One motor race held on 3 November 1991 at the Adelaide Street Circuit. It was the 16th and final race of the 1991 Formula One World Championship. Torrential rain resulted in the race being stopped after just 16 of the scheduled 81 laps had been completed. The official results were declared from the end of the 14th lap, two laps before the race was suspended, in line with regulations. It holds the record for being the shortest Formula One World Championship race that was legally conducted under modern rules; the 2021 Belgian Grand Prix, which ran two aborted formation laps that did not count and three laps under the safety car before it was red-flagged (two of which did not count under the countback rule), does not count under the post-2022 rule changes. From a timing standpoint, it is the shortest Formula One World Championship race in history, as the race lasted barely 30 minutes from formation lap to abandonment. (The 2021 Belgium race started with two formation laps began at 15.25, then delayed until 18.15 and abandoning the attempt at 18.25 after three more laps.)
The race was won by Ayrton Senna, with Nigel Mansell in second position, and Gerhard Berger's third-place finish plus Senna's victory meant that the McLaren team clinched the Constructor's championship. Mansell was unable to take part in the post-race podium ceremony, following a crash at the end of the race that left him requiring hospital treatment. Because less than seventy-five percent of the scheduled race distance had been completed, only half the normal World Championship points were awarded. This was also the final Formula One race for three time World Champion Nelson Piquet. It was the 60th pole position for Ayrton Senna. It would also prove to be the final Grand Prix for Satoru Nakajima, Naoki Hattori, Alex Caffi, and Emanuele Pirro, and was the last race with Pirelli tyres until the 2011 Australian Grand Prix.
Pre-race
Ferrari terminated Alain Prost's contract with the team following his public criticism of them. His raceseat was taken by Gianni Morbidelli, the Ferrari test driver. After being dropped by the Jordan team two races earlier, Roberto Moreno returned to Formula One to take Morbidelli's place at Minardi. Benetton did not renew Nelson Piquet's contract with the team, and Australia would be his last Formula One race. Bertrand Gachot returned to Formula One after completing his jail sentence in Britain, replacing Éric Bernard at Larrousse, who had been injured at the previous race meeting in Japan. The Coloni team were entered for their final Grand Prix; new owner Andrea Sassetti had confirmed that the team would be reborn as Andrea Moda Formula for the following season. Williams also had a 'B'-spec version of the FW14 present, but elected not to use it in the race.
Qualifying
Pre-qualifying report
The one-hour pre-qualifying session took place in sunny and dry conditions on Thursday afternoon, instead of Friday morning to expand the race meeting to four days. The session resulted in the Brabham and Footwork teams getting their cars through to the main qualifying sessions, with Martin Brundle's Brabham three tenths of a second faster than Alex Caffi's Footwork. Mark Blundell was just four hundredths of a second behind in the other Brabham, with Michele Alboreto's Footwork just 0.002 of a second slower in fourth.
Gabriele Tarquini narrowly failed to pre-qualify for Fondmetal as his track time was limited after a left rear suspension failure on the exit of turn 11, which turned his car into the wall. It was his first failure to pre-qualify for Fondmetal in three attempts. Slowest was Naoki Hattori in the Coloni, over five seconds away from Brundle's pace. Coloni had failed to pre-qualify for every race in 1991, their last season at the highest level.
Riccardo Patrese was struggling with his car because a front wing, from another car, got stuck towards the front of his undertray. This was spotted by James Hunt in the BBC race commentary, although Murray Walker had suggested earlier that it was the undertray that was loose. Mansell then, as a result of the increasing downpour, spun off on the start of lap 16 on the Wakefield Road straight, before turn 3, having "instantly gone out of control" according to Mansell himself. The torrential downpour also made Michele Alboreto spin out of the race on lap 15 as well as Modena, although he continued. Nelson Piquet also spun at the high-speed Stag turn but was able to recover and he continued as well.
Gerhard Berger spun off at the end of lap 16 having just recovered from an earlier spin at the Malthouse Corner moments before. Murray Walker said that the weather was becoming worse and the rain was lashing down on the start/finish line. Just after this happened Senna drove onto the start/finish straight and gestured to the race officials, as he went past, to try to get the race stopped. Moments later, with Senna on lap 17, the race was finally stopped. By the end of lap 16 the race order actually was Senna in 1st from Piquet, Morbidelli, de Cesaris, Zanardi and Modena. However, the race officials decided to count back to lap 14 despite the 1991 ruling that early race stoppages should have been counted back one lap. This incident was similar to the controversy of the 2003 Brazilian Grand Prix, where computers finalising the race concluded the result a lap too early.
There were attempts to restart the race from the officials, who showed their determination to do so by ordering the 10-minute warning board to be displayed to the drivers and teams to indicate a race restart.
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Final championship standings
;Drivers' Championship standings
{|class="wikitable" style="font-size: 95%;"
|-
!
! Pos
! Driver
! Points
|-
|align="left"| 10px
|align="center"| 1
| Ayrton Senna
|align="right"| 96
|-
|align="left"| 10px
|align="center"| 2
| Nigel Mansell
|align="right"| 72
|-
|align="left"| 10px
|align="center"| 3
| Riccardo Patrese
|align="right"| 53
|-
|align="left"| 10px
|align="center"| 4
| Gerhard Berger
|align="right"| 43
|-
|align="left"| 10px
|align="center"| 5
| Alain Prost
|align="right"| 34
|-
!colspan=4|Source:
|}
;Constructors' Championship standings
{|class="wikitable" style="font-size:95%;"
|-
!
! Pos
! Constructor
! Points
|-
|align="left"| 10px
|align="center"| 1
| McLaren-Honda
|align="right"| 139
|-
|align="left"| 10px
|align="center"| 2
| Williams-Renault
|align="right"| 125
|-
|align="left"| 10px
|align="center"| 3
| Ferrari
|align="right"| 55.5
|-
|align="left"| 10px
|align="center"| 4
| Benetton-Ford
|align="right"| 38.5
|-
|align="left"| 10px
|align="center"| 5
| Jordan-Ford
|align="right"| 13
|-
!colspan=4|Source: