The first three generations of the WRX were built on standard Impreza platforms. The original first-generation models were based on the Impreza saloon (GC chassis), followed by wagons (GF) in 1993. The high-performance WRX STI variant arrived in 1994. Several limited-edition first-generation coupes were produced in the late 1990s and early 2000s and were never sold in the United States, making them highly sought after by collectors.
The second generation (GD/GG chassis for saloon and wagon) reached the North American market for model year 2002, with the STI following for model year 2004. The styling evolved through the "bugeye" front end of 2000, the "blobeye" of 2004, and the "hawkeye" of 2006. During this period, under an agreement between Fuji Heavy Industries and General Motors, Saab sold a version of the WRX wagon as the Saab 9-2X for the 2005 and 2006 model years.
The third generation used GE (saloon) and GH (hatchback) chassis codes, with the WRX STI available only as a wide-body hatchback (GR). From the 2011 model year, both STI variants moved to widened GV and GR platforms. A redesigned fourth-generation Impreza appeared for 2012, at which point the WRX continued on the third-generation GV/GR chassis through the 2014 model year in most markets.
Starting with the 2015 model year (VA chassis), Subaru officially separated the WRX from the Impreza nameplate. In Japan the car was sold as the WRX S4. The VA-generation WRX departed from the previous EJ-series boxer engine and adopted the new FA20F 2.0-litre direct-injection turbocharged unit with a twin-scroll turbocharger. The FA20F produces 268 hp in international specification and 295 hp in the Japanese-spec WRX S4. A 6-speed manual transmission was standard, with a Lineartronic CVT available on the WRX but not on the STI.
The WRX STI retained the EJ-series engine from the prior generation: the 2.5-litre EJ257 for international markets, rated at 305 hp, and the 2.0-litre EJ207 (300 hp) for Japan. The STI kept hydraulic power steering and a 6-speed TY85 manual.
Numerous limited-edition variants were produced during the VA era: the 1,000-unit WRX STI Launch Edition (2015, World Rally Blue with gold BBS wheels), the Japanese-market S207 (400 units), S208 (450 units), and the RA-R; the US-market WRX STI Type RA (500 units); the Canadian Raiu Edition (100 units) and Kanrai Edition (75 units); the WRX Series.Gray and Series.White; and the S209 (209 units), the first S-series STI sold in the United States, priced at $64,000 and producing 341 hp from a modified EJ257.
A special EJ20 Final Edition (555 units, Japan only) was produced in late 2019 to mark the end of the EJ20 engine, featuring precision-balanced internals built to near-racing tolerances.
The second-generation standalone WRX (VB chassis) debuted for the 2022 model year, built on the Subaru Global Platform. It uses the FA24F 2.4-litre turbocharged boxer producing 271 hp and 258 lb-ft of torque, paired with either a six-speed manual or a new Subaru Performance Transmission CVT. Subaru confirmed there would be no WRX STI with an internal-combustion engine in the VB generation, citing rapidly changing emissions regulations. A future WRX STI is expected to feature hybrid or battery-electric power.
The Subaru Impreza WRX became inseparable from Subaru's dominant WRC factory programme in the 1990s. The Subaru World Rally Team, run by Prodrive, won three consecutive drivers' championships with Colin McRae (1995), Carlos Sainz (1996 in the WRC equivalent year), and Richard Burns (2001), and captured manufacturers' titles across that era. The car's distinctive blue livery with gold wheels — colours tied to a sponsorship arrangement — became one of the most recognisable colour schemes in motorsport. The road-going WRX was engineered to share key structural and mechanical elements with the rally cars, making it one of the closest connections between a homologation road car and a championship-winning rally machine in the sport's history.