Unveiled at the 2014 Detroit Auto Show, the independent generation of the flagship Subaru WRX STI (VA platform) launched alongside the WRX sedan. Power was provided by the proven 2.5-liter EJ257 turbocharged flat-four engine producing 305–310 hp (or the 2.0-liter EJ207 producing 308 hp in Japan), paired exclusively with a reinforced 6-speed manual transmission. The engineering setup effectively combined the low center of gravity inherent to the horizontally-opposed engine layout with a rigid chassis frame, delivering precise handling and composure across dry pavement and slippery surfaces alike. Engine bay packaging ensured optimal front-to-rear axle weight distribution alongside efficient thermal cooling under sustained driving loads.

The STI incorporated Subaru's Multi-Mode Driver Control Center Differential (DCCD) Symmetrical AWD system with front and rear limited-slip differentials, high-performance Brembo brakes, and a iconic large rear wing. A 2017 facelift upgraded the braking system to 6-piston yellow Brembo calipers and 19-inch wheels. Dedicated WRX STI production concluded in 2021. Designers placed a strong emphasis on cabin ergonomics, occupant visibility, and long-distance driving comfort. Robust mechanical reliability across the drivetrain and suspension components helped establish this generation as a benchmark choice within its competitive market segment worldwide.