The 1990 24 Hours of Le Mans was the 58th Grand Prix of Endurance, taking place at the Circuit de la Sarthe, France, on the 16 and 17 June 1990. Due to the ongoing dispute between the ACO and the FISA governing body, the race was not part of the World Sports-Prototype Championship. This was the last Le Mans run under the Group C formula, and a number of manufacturers put in a major effort to win, with the notable exception of defending winners Sauber-Mercedes.

Fitted with a special qualifying engine, Mark Blundell put in a blistering lap to put his Nissan on pole, fully six seconds faster than Oscar Larrauri in the Brun Porsche. Those two cars set the pace in the opening hours. That Porsche was the interloper of an exciting Jaguar versus Nissan battle. The first major incident of the race was in the early evening when the Gianfranco Brancatelli in the race-leading Nissan clipped the Toyota of Aguri Suzuki as they passed by the pits at full speed. The Toyota was wrecked but Suzuki emerged with only some bruising. The only full-course caution was at midnight when another accident sent the Lancia of Fabio Magnani into the trees by the circuit. Again, the driver could walk away. During all this, the Nissan-Jaguar-Brun contest continued unabated through the night.

As Sunday dawned, the Jaguar of Cobb and Nielsen had a 1-lap lead over the IMSA-based Nissan of Brabham/Robinson/Daly. However, at breakfast time, the Nissan challenge faded when Daly brought the car in with a fuel leak. Brundle's car had retired a few hours earlier and he had transferred into the lead car. Meanwhile, the Brun Porsche had stayed in contact and moved up to second. The chase continued all morning, with the Jaguar nursing a damaged gearbox, still just a lap ahead. Then in a cruel twist of luck, with barely a quarter hour to run, the engine broke on the Porsche and it sputtered to a stop at the Mulsanne hairpin. Jaguar inherited a fortuitous 1-2 victory, with Cobb/Nielsen/Brundle heading home previous winners Jan Lammers and Andy Wallace with Franz Konrad. Third was the best of the Porsches, the new Alpha team from Japan, which had one of the few trouble-free races among the finishers.

This was the second transition year as FISA (Fédération Internationale du Sport Automobile) moved on from Group C to its 3.5-litre formula. These non-turbo engines were intended to be closely aligned to the Formula 1 regulations to encourage "cross-pollination" by engine manufacturers. However, they were by design "sprint" engines unsuited to endurance racing. FISA therefore planned for all races to only be run over 300 miles, with Le Mans to be the sole exception. The ACO (Automobile Club de l'Ouest) had already had intractable disagreements with FISA in 1989 that resulted in Le Mans being thrown out of the World Championship. These arguments carried on throughout the rest of the year, as FISA tried to push to get their timekeeping and media rights imposed across the organising groups. The FIA even briefly threatened to revoke the racing licenses of drivers that ran at Le Mans. The racing license for the Circuit de la Sarthe was due at the end of the year, and FIA/FISA president Jean-Marie Balestre was prepared to use that as leverage with the ACO. Another target was the Ligne Droite des Hunaudières – at 5.7 kilometres, the Hunaudières straight was the longest straight in motorsport, and in the last two years both WM and Sauber-Mercedes cars had famously reached the 400 km/h (248 mph) barrier. In December, Balestre approached the World Motor Sport Council. His proposal was to limit the length of any straight to no more than 2 km (1.2 miles), ostensibly in the interests of safety. It was passed unanimously, coming into effect from 1990. The ruling decreed no circuit licensed by FISA may have a straight longer than 2 km. The ACO unsuccessfully appealed to the French courts and were therefore obliged to buy land and install two, roughly equidistant, chicanes along the Hunaudières straight to make it comply to the new decree. In total, they added 65 metres to the lap distance – taking it to 13.600 km (8.45 miles). Works were also done to create a new, twisty, pit-entry road designed to dramatically slow the cars down coming into the crowded pit-lane. As the works were completed in February, after the FISA deadline had lapsed, the Le Mans 24-hours would again be excluded from the World Championship. Nissan management believed the chicanes would slow lap-times by about 20 seconds, or 10%, and the overall distance covered by a similar amount, however they thought fuel consumption would stay about the same.

This had a follow-on effect on the car regulations. Manufacturers and teams knew as the season started that Le Mans would not be included and could plan accordingly. Likewise, the ACO was no longer bound by the official rules that heavily penalised the Group C cars with a minimum weight of 1000 kg. They retained the 900 kg for Group C, against the 750 kg minimum of the 3.5-litre 'atmos'. The latter had no fuel restriction; however, the Group C were still limited to 2550 litres. The C2 class had been abolished in the new championship, but the ACO opened up entries to the class, keeping the 750 kg / 1815-litre restrictions of the previous year. The GTP class had the same fuel allowance as Group C but used the IMSA sliding-scale, weight-to-engine-size chart.

Qualifying was again on Wednesday and Thursday, with 2½ hours daylight and 2 hours night running each day. All drivers had to do a lap-time within 120% of the average of the fastest three cars, as well as doing at least three laps at night. Times done in a team's Test-car would now also be officially accepted, which would allow teams to wind up the turbos on "disposable" engines for one-off high-power qualifying laps. During the race, night was defined as between the hours of 9pm and 4.30am. Drivers were only allowed to drive a maximum of 14 hours total, with no stint lasting longer than 4 hours and a minimum 60-minute stand-down between shifts. They could switch between cars of the same team but only three drivers were allowed per car.

Pit rules were stipulated as follows:
- There was an 80 km/h (50 mph) speed limit in the pit-lane;
- A maximum of four pit-crew could work on a car at a time;
- Engines had to be switched off during refuelling, and wheel changes only happened after the refuelling was completed
To be qualified as a finisher, a car had to pass the chequered flag under its own power, and complete a total distance of at least 70% of the winner.

Even though this was a phase-out, interim season, a top-quality field of Group C presented their entries to the ACO. There were 41 cars at scrutineering, including a massive 20 Porsches. Works teams came from Jaguar, Porsche, Nissan, Toyota and Mazda. However, the big news was that Sauber-Mercedes would not return to defend their victory, as it was a non-Championship round. There were only three cars entered for the upcoming FIA 3.5-litre class. Once again, the C2 class was dominated by Spice with 6 of 11 entries. This year there was a significant Japanese presence. There were 19 cars made in Japan; and along with the three works teams, there were seven teams from their national championship and 15 drivers from that country.