The Audi R8 is a Le Mans Prototype sports-prototype race car introduced in 2000 for sports car racing as a redevelopment of their Audi R8R (open top LMP) and Audi R8C (closed top LMGTP) used in 1999. In its class it is one of the most successful racing sports cars having won the 24 Hours of Le Mans race in 2000, 2001, 2002, 2004, and 2005, five of the six years it competed in total.

Its streak of Le Mans victories between 2000 and 2005 was broken only in 2003 by the Bentley Speed 8, another race car fielded that year by Volkswagen Group.

The petrol-powered Audi R8 race car was in 2006 replaced by the new Audi R10 TDI Diesel. However, the need to further develop the R10 meant that the R8 saw action in a few races leading up to the 24 Hours of Le Mans.

The R8 is powered by a 3.6 L Audi FSI V8. FSI stands for Fuel-Stratified Injection, which is a variation on the concept of gasoline direct injection developed by Volkswagen which maximizes both power and fuel economy at the same time. FSI technology can be found in products available to the normal public, across all brands in the Volkswagen Group.

The power supplied by the R8, officially listed at about 610 hp (455 kW) in 2000, 2001 and 2002, 550 hp (410.1 kW) in 2003 and 2004 and 520 hp (388 kW) in 2005, is sent to the rear wheels via a Ricardo six-speed sequential transmission with an electro-pneumatic gear change.

Unofficially, the works-team Audi R8 for Le Mans (2000, 2001 and 2002) is said to have had around 670 hp (500 kW) instead of the quoted 610 hp (455 kW). The numbers were quoted at speed, and were due to the car making 50 extra horsepower due to twin ram-air intakes at speeds over 150 mph (240 km/h).

Official torque numbers were quoted for this version of the engine at 516 lb.ft (700 Nm) at 6500 rpm. The equation for horsepower (torque divided by 5250, multiplied by rpm) for these numbers produces a horsepower rating of 638 horsepower (476 kW) at the same 6500 rpm (516/5250*6500=638).

The Audi R8's structure was designed from the very beginning to expedite parts changes during the race. The car has a chassis that has been likened to a Lego model – anything on the car can be changed and changed quickly.

During its campaign, the Joest pit crew was able to change the entire rear transaxle of a damaged R8 – a process which usually takes between one and three hours – in as low as three minutes and 16 seconds.

The reason for this was that the transmission, rear suspension and rear subframe were built as one unit. The car had numerous quick-connect hoses and easily removable bolts. The whole rear section of the car could be removed as a whole and a new back half installed with the help of a crane.

The Automobile Club de l'Ouest (ACO), organizers of the 24 Hours of Le Mans and the American Le Mans Series acted quickly to void this advantage by mandating the gearbox casing be the same item through the duration of the race, with only the internals being allowed to be changed.

However, the R8 still had quicker access to the gearbox internals than any other car due to its quick-change construction. This was critical as the gearbox was the weak link in the car.

The R8's structure and body are both composed of carbon fibre, a strong, lightweight polymer material. Performance – from top speed to acceleration – was, as in most race car cases, variable depending on the car's setup.

The highest speed of the R8 at Le Mans was 338 km/h (210 mph) in the practice sessions of the 2002 Le Mans 24 Hours Race. A low downforce setup could generate about 350 km/h (217 mph).

Audi Sport's program saw tragedy in 2001 when on April 25, popular ex-F1 driver Michele Alboreto died in an accident after suffering a high-speed tyre failure during an R8 test session at the Lausitzring in eastern Germany.

The Bentley Speed 8, which ran at Le Mans from 2001 to 2003, winning in 2003, utilised a heavily modified 4.0 L version of the V8 engine from the Audi R8. The Bentley racing effort was campaigned by Team Bentley (Apex Motorsport) with assistance from longtime R8 competitor Joest Racing and Audi Sport UK.

After 2002 the Joest factory team dropped its R8 campaign and left it to the privateers. Restrictor changes brought the power down to 550 bhp for anyone still racing with the R8, however the maximum torque hardly changed.

Tom Kristensen, who won the previous three 24 Hours of Le Mans races in an R8, was assigned to drive the Bentley Speed 8, and helped guide the team to victory. There is some similarity between the Bentley Speed 8 and the Audi R8's successor, the R10 TDI.

During the 2005 season, it was evident that its time at the front of the pack was drawing to a close. Audi had made the development of the Audi R10 TDI diesel public, and cars from other manufacturers and teams started to catch up in terms of on-the-track speed.

The ACO still felt that the R8 needed to be kept in check, therefore they reduced the restrictor size on the R8's engine, due to the car not meeting new hybrid regulations, and stipulated the car shall carry ballast weight in an attempt to make the races more competitive. The R8 was restricted even further to only 520 bhp.

At the 2005 Le Mans, the Audis failed to qualify on pole position; the fastest R8 started the race in third position. However, the car was able to outlast all other competitors to eventually take its fifth checkered flag at the Circuit de la Sarthe and the 24 Hours of Le Mans.

This victory was also notable since it was Tom Kristensen's 6th straight 24 Hours of Le Mans victory, and a record 7th overall, beating legendary driver Jacky Ickx's previous record of 6 career 24 Hours of Le Mans victories. To date the R8 remains one of the fastest petrol powered LMPs, setting a 3:29 at Le Mans, which was beaten only by the Lola-Aston Martins. However, the R8's best finish was at 379 laps, which is more than the Lola-Aston Martin's best at 373 laps.

In response to the new level of competition, development of the successor, known as the Audi R10 TDI, has been completed. The V12 engined turbodiesel won at its race debut at the 2006 12 Hours of Sebring with both cars starting on the front row. However, the pole sitting R10 had to start from the pit lane due to the need to rectify heat exchanger issues.

Emanuele Pirro, Frank Biela and Marco Werner made history by becoming the first drivers to win the Le Mans 24-hour race in a diesel-powered car. The Audi R10 TDI completed a record 380 laps of the La Sarthe circuit, with Pirro at the wheel for the finish. French trio Sébastien Loeb, Éric Hélary and Franck Montagny took second in the Pescarolo Judd No 17, four laps adrift. Scotsman Allan McNish was third in the other Audi, which came in 13 laps down after suffering mechanical problems.

The R8 continued to campaign the American Le Mans Series through the first half of the 2006 season, and made its final US appearance on July 1, 2006 at Lime Rock Park, Connecticut, piloted by McNish and Capello. The R8 ended its career in style by winning the race, the 50th American Le Mans Series win for the Audi R8. The R10s participated in the rest of the ALMS season, beginning with the race at Miller Motorsports Park, Utah.

The name Audi R8 also is used by the production road sports car Audi R8 which is based on the 2003 Audi Le Mans quattro concept car, and the R8 race car experiences. Production started in 2007.