Car tuning is a generalized term to refer to the act of improving the performance or appearance of a vehicle. For actual "tuning" in the sense of automobiles or vehicles, see engine tuning. As most vehicles leave the factory set up for average driver expectations and average conditions, tuning has become a way to personalize the characteristics of the vehicle to the owner's preference. For example, cars may be altered to provide better fuel economy, produce more power, or to provide better handling.

Car tuning is related to auto racing, although most performance cars never compete. Rather, they are built for the pleasure of owning and driving such a vehicle. Exterior modifications include changing the aerodynamic characteristics of the vehicle via side skirts, front and rear bumpers, spoilers, splitters, air vents and light weight wheels.

In the 1970s and 80s, many Japanese performance cars were never exported outside the Japanese domestic market. In the late 1980s and early 1990s, grey imports of Japanese performance cars, such as the Nissan Skyline, began to be privately imported into Western Europe and North America. In the United States, this was in direct contrast to the domestic car production around the same time, where there was a very small performance aftermarket for domestic compact and economy cars; the focus was instead on sporty cars such as the Ford Mustang and Chevrolet Corvette, or on classic muscle cars.