A continuously variable transmission (CVT) is a type of automatic transmission that varies the distance between a pair of belt or chain-linked pulleys, wheels or cones to smoothly alter its gear ratio without requiring any predefined steps or sudden changes in engine speed.

Continuously variable transmissions operate on the theory of pulleys; a large pulley connected to a smaller pulley with a belt or chain will operate in the same manner as a large gear meshing with a smaller gear. Typical CVTs have two opposing, cone shaped drums in them (one on the input, one on the output side) which can be moved in and out, controlled by the engine vacuum in the inlet manifold and engine RPM and centrifugal force acting on weights inside the conical drums. Moving the cones in and out has the effect of changing the driving and driven pulleys' diameter, thus changing the gear ratio. As there are no predefined steps in the system, it's referred to as continuously variable.

Some continuously variable transmissions instead use a variable displacement pump and a hydraulic motor to transmit power. These types can generally transmit more torque, but they are very expensive to buy and maintain. However, they have the advantage that the hydraulic motor can be mounted directly to the wheel hub, allowing a more flexible suspension system and eliminating efficiency losses from friction in the drive shaft and differential components.