The Audi R18 is a Le Mans Prototype (LMP) racing car constructed by the German car manufacturer Audi AG.
It is the successor to the Audi R15 TDI. Like its predecessor, the R18 uses a TDI turbocharged diesel engine but with a reduced capacity of 3.7 litres and in a V6 configuration.
For the first time since the 1999 R8C, Audi's Le Mans prototype uses a closed cockpit design.
The R18 is also the first racing car from Audi to feature hybrid power.
The R18 e-tron quattro is a hybrid version of the R18 ultra, with a 500 kJ flywheel accumulator system designed by Williams Hybrid Power, two 101 PS (74 kW; 100 hp) Bosch Motor Generator Units driving the front wheels with water-cooled integrated power electronics, providing the car with four (quattro) wheel drive, and a smaller 58-litre fuel tank.
The quattro system, as per regulations, is available only at speeds above 120 km/h (75 mph).