The concept for Group GT3 was introduced by Stéphane Ratel, head of the SRO Group, to simplify the process of building and developing racing cars compared to the more costly Group GT1 and Group GT2 categories. GT3 was envisioned to combine existing cars from one-make series, such as the Porsche Supercup and Ferrari Challenge, alongside other race cars not fitting into GT1 or GT2, like the Aston Martin DBRS9 and Dodge Viper Competition Coupe. The goal was to create a level playing field through strict performance control by the FIA, offering drivers a bridge between national series and the professional FIA GT Championship.
GT3 cars must be based on mass production road car models being built and sold at the time of homologation, though this requirement does not necessarily include the engine. For example, the BMW Z4 GT3 used the 4.0L V8 from the BMW M3 E92, while the Mercedes-AMG GT3 utilized the 6.2 V8 from the Mercedes SLS AMG GT3. Performance is regulated through balance of performance formulae that adjust limits on horsepower, weight, engine management, and aerodynamics to prevent a single manufacturer from becoming dominant. Cars are designed to weigh between 1,200 and 1,300 kilograms with output between 500 and 600 horsepower. All cars feature a similar power-to-weight ratio, achieved either through high power and high weight (such as the Mercedes-Benz SLS AMG) or low power and low weight (such as the Porsche 911 GT3). GT3 cars also feature traction control, ABS, and built-in air jacks for quick pit stops.
The regulations and homologations for Group GT3 were prepared by the FIA and ready for the 2006 season, with eight manufacturers represented in the initial Balance of Performance testing. Several championships, including the International GT Open, British GT Championship, Spanish GT Championship, and Italian GT Championship, created categories specifically for the new machines. The French FFSA GT Championship also added a new GT3 category. The SRO Group expanded the category in 2007 with the launch of the Brazilian GT Championship and the German ADAC GT Masters. The British GT Championship promoted GT3 to its premiere category, and the Belcar series introduced GT3 as its lead class.
The Australian GT Championship brought on board the GT3 category in 2008, while the VLN Series and 24 Hours Nürburgring added GT3 categories in 2009. Group GT3 later expanded into endurance racing with the formation of the Blancpain Endurance Series and overall victories at the Bathurst 12 Hour, Dubai 24 Hour, Malaysia Merdeka Endurance Race, and Spa 24 Hours. The category also expanded to the United States with the Rolex Sports Car Series and to Japan with the Super GT and Super Taikyu Series; Nissan became the first Japanese manufacturer to sell a GT3 car. GT3 cars replaced Group GT1 cars in the FIA GT1 World Championship before rebranding as the FIA GT Series in 2013. Following the merger of the Grand-Am Rolex Sports Car Series and the American Le Mans Series, the new United SportsCar Championship allowed GT3 cars to join the GTD category, limiting it to GT3-spec machines by 2016.
In 2018, the FIA approved a new process requiring minimum production numbers: ten units must be made within twelve months of the homologation date, and twenty units within twenty-four months. In 2021, the Deutsche Tourenwagen Masters (DTM) switched to the GT3 formula, abandoning its touring car origins. In 2022, the FIA confirmed that GTE cars in the FIA World Endurance Championship would be replaced by GT3 cars in the LMGT3 class, allowing participation in the 24 Hours of Le Mans from 2024 onward.
As of April 2026, 59 vehicles have gone through the FIA homologation process. Homologations expire after seven years unless an extension is requested. Currently, all homologations prior to GT3-030 have expired, though these cars may compete in national series under local approval or in historic events. One such championship, the GT3 Revival Series, uses cars homologated between 2006 to 2009 and 2010 to 2013, which are classified as "Gen I" and "Gen II," respectively. As of January 2026, 19 vehicles hold valid FIA homologation for competition.
As premier class ADAC GT Masters, Deutsche Tourenwagen Masters, FIA GT World Cup, GT3 Legends (gen 1 only), GT Revival Series (older models only), GT World Challenge (America, Australia, Asia, Europe), Intercontinental GT Challenge, International GT Open, Italian GT Championship.
As subsidiary class FIA World Endurance Championship (LMGT3), IMSA SportsCar Championship (GTD and GTD Pro), 24H Series, Asian Le Mans Series, Belcar, British GT Championship, European Le Mans Series, GT America Series, Michelin Le Mans Cup, Nürburgring Langstrecken Serie, Super GT, Super Taikyu Series, Trans-Am Series.