Group GT3, known technically as Cup Grand Touring Cars and commonly referred to as simply GT3, is a set of regulations maintained by the Fédération Internationale de l'Automobile (FIA) for grand tourer racing cars designed for use in various auto racing series throughout the world. The GT3 category was initially created in 2005 by the SRO Group as a third rung in the ladder of grand touring motorsport, below the Group GT1 and Group GT2 categories which were utilized in the SRO's FIA GT Championship, and launched its own series in 2006 called the FIA GT3 European Championship. Since then, Group GT3 has expanded to become the de facto category for many national and international grand touring series, although some series modify the ruleset from the FIA standard. By 2013, nearly 20 automobile manufacturers have built or been represented with GT3 machines.

A grand tourer (GT) is a type of car that is designed for high speed and long-distance driving due to a combination of performance and luxury attributes. The most common format is a front-engine, rear-wheel-drive two-door coupé with either a two-seat or a 2+2 arrangement. Grand tourers are most often the coupé derivative of luxury saloons or sedans. Many iconic car models, such as the Ferrari 250 GT, Jaguar E-Type, and Aston Martin DB5, are considered classic examples of gran turismo cars.