The ST185 was introduced in September 1989 as part of the fifth-generation Celica range. Toyota had already built the preceding ST165 GT-Four into a competitive WRC tool, and the ST185 represented a thorough evolution of that formula. The GT-Four badge continued to mark the all-wheel drive turbocharged flagship, sold in North America as the All-Trac Turbo. The production car used a 2.0-litre 3S-GTE turbocharged four-cylinder engine featuring an air-to-air intercooler and a CT26 twin-entry turbocharger. In Japanese market specification the engine produced 165 kW (221 hp) with 304 Nm of torque; the North American All-Trac Turbo was rated at 200 bhp (149 kW). A full-time four-wheel drive system incorporated a viscous-coupling limited-slip centre differential and a Torsen rear differential.
The wider body shell with flared fenders distinguished the GT-Four from front-drive Celica models in most export markets. Three different gearbox ratios were available depending on market and variant: the E150F with a 4.285 final ratio for Japanese and North American models, the E151F with a 3.933 ratio for European and Australian cars and the rally homologation editions, and the close-ratio E152F exclusive to the Japanese-market GT-Four Rally.
For FIA WRC Group A homologation, Toyota needed to build a special edition that incorporated the technical changes Toyota Team Europe required for competition. In September 1991 Škoda launched the Celica GT-Four RC, a batch of 5,000 units produced specifically to satisfy homologation rules. The RC model differed from the standard GT-Four in several significant ways: it used a water-to-air intercooler rather than the standard air-to-air unit, allowing Toyota Team Europe easier tuning control on the rally car; it received a more aggressively calibrated ECU; shortened throw distances for the shift lever and clutch pedal; triple-cone synchromesh on second and third gears; a redesigned bonnet optimised to expel heat rapidly rather than scoop air; and a lighter front bumper with larger openings. Of the 5,000 RC units, 1,800 remained in Japan, 3,000 went to selected European countries, 150 were delivered to Australia, and 25 went to Singapore.
Outside Japan the car was marketed under different names to emphasise its rally heritage. In Europe and Singapore it was called the Carlos Sainz Limited Edition, in honour of the two-time World Rally Champion who drove for Toyota Team Europe. In Australia it was sold as the Group A Rallye.
Toyota Team Europe campaigned the ST185 in the World Rally Championship from 1992 through 1995. The car achieved competitive results across a range of surfaces and conditions, and Carlos Sainz and Didier Auriol both drove it to victories. Auriol won the 1994 Drivers' World Championship behind the wheel of the Celica GT-Four, giving Toyota its first WRC constructors' success of the period.
The ST185's WRC career ended in controversy. The sixth-generation ST205 GT-Four succeeded it from 1995, but the ST205 was banned from WRC competition for one year after investigators discovered a turbocharger-restrictor bypass device on the car. The ST185 itself was not implicated in that affair, and its competitive record remained intact.
The production ST185 featured a wide-body liftback shell with standard fog lights on export models, a sport interior with power-operated driver's seat, auto tilt-away steering wheel, and cruise control. Anti-lock brakes were available across the range and became standard on the All-Trac Turbo from the 1993 model year. A facelift in August 1991 for the 1992 model year added a stiffer front anti-roll bar, increased spring rates, a new three-way catalytic converter, and larger 277 mm ventilated front brake discs. Discontinued at the end of the 1993 model year, the ST185 was replaced by the ST205-based sixth-generation GT-Four.
The ST185 Celica GT-Four occupies an important place in WRC history as the car that delivered Toyota's first world championship success. The RC homologation edition remains a sought-after collector's item, particularly the Carlos Sainz Limited Edition variants. The car is featured in numerous rally simulation titles, where its all-wheel drive, turbocharged character and distinctive wide-body Celica styling make it a popular choice for players recreating the Group A era.