A kit car, also known as a component car, is an automobile that is available as a set of parts that a manufacturer sells and the buyer himself then assembles into a functioning car. Usually, many of the major mechanical systems such as the engine and transmission are sourced from donor vehicles or purchased new from other vendors. Kits vary in completeness, consisting of as little as a book of plans, or as much as a complete set with all components included.
There is a sub-set of the kit car, commonly referred to as a "re-body", in which a commercially manufactured vehicle has a new (often fiberglass) body put on the running chassis. Most times, the existing drive gear and interior are retained. These kits require less technical knowledge from the builder, and because the chassis and mechanical systems were designed, built, and tested by a major automotive manufacturer, a re-body can lead to a much higher degree of safety and reliability.
The definition of a kit car usually indicates that a manufacturer constructs multiple kits of the same vehicle, each of which it then sells to a third party to build. A kit car should not be confused with a 'hand built' car or 'special' car, which is typically built from scratch by an individual.