Quattro is a permanent all wheel drive system used on Audi brand automobiles. Quattro was first introduced in 1980 on the Audi Quattro Coupé based on the Audi 80 and has since been deployed to most of the models that Audi sells.

In the original Quattro system, where the engine and transmission are situated in a longitudinal position, power is sent from the transmission to a mechanical center Torsen differential which splits it between the front and rear axles. Under ideal conditions power is split 50/50 front to rear. The 50/50 split helps prevent wheel slip from starting, which is better than systems that can only react after wheel slip starts. In extreme cases, up to 67% of the engine's power can be directed to a single axle. The power split between left and right wheels has progressed through open, lockable and eventually limited slip differentials with electronic control. The system allows propulsion even if only one wheel has traction. This system is also available in the B5 Passat under the name 4motion .

In some recent Audi models using a transverse engine and transmission positioning, power is sent primarily to the front axle, however an electrohydraulic center Haldex limited slip coupler may divert up to 100% of the power to the rear axle as conditions warrant. This action causes a sudden jolt which may break traction on the wheels that still have it. The power split between left and right wheels is achieved through limited slip differentials with electronic control. This system is also available in most Volkswagen vehicles under the name 4motion , excluding the B5 Passat.

Quattro is a registered trademark of Audi AG.