A continuously variable transmission (CVT), (also known as single-speed transmission, gearless transmission, one-speed automatic, variable pulley transmission, or in case of motorcycles, a twist-and-go) is a transmission that can change seamlessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios. The flexibility of a CVT allows the input shaft to maintain a constant angular velocity.

A belt-driven design offers approximately 88% efficiency,[1] which, while lower than that of a manual transmission, can be offset by lower production cost and by enabling the engine to run at its most efficient revolutions per minute (RPM) for a range of vehicle speeds. Thus a small car can strike a balance between fuel efficiency and cost of manufacture.