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 held the record for being the shortest Formula One World Championship race until the 2021 Belgian Grand Prix. 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 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.