Automotive News reports the announcement was made earlier this week at the technical day of the Audi Forum in Munich.
The mild hybrid setup includes a belt-driven alternator/starter, and a 48V lithium-ion battery that's recharged via regenerative braking. The system will be standard on both Audi A8 diesel and petrol models.
Audi says the system can provide up to 12kW of power and 60Nm of torque. It's claimed, under the NEDC testing scheme, fuel economy can be improved by up to 0.7 litres per 100 kilometres.
In the A8, the mild hybrid system will allow the car to coast with the engine off at speeds between 30 and 160km/h. A front-facing camera will help the A8 decide when it's best to switch the engine off.
Higher-spec models will also use predictive data from the satellite navigation and various vehicle sensor systems as part of its decision making process.
A traditional 12V battery will still be used to power the car's lighting, air conditioning, engine management and other systems.
Alexander Kruse, Audi's head of mild hybrid systems, told the industry publication, use of the 48V setup will spread "very quickly" throughout the brand's range.
The fourth-generation A8 will make its debut on July 11, European time.