The Lexus GS (S190) is the third generation of the Lexus GS line of executive cars. Sold by Lexus from 2005 to 2011, the line includes multiple V6, V8, and hybrid models. A concept model for the GS line, the LF-S, debuted in late 2003 at the Tokyo Motor Show. The third generation GS first appeared as a pre-production vehicle at the 2004 North American International Auto Show in Detroit with the production version being shown a year later at the 2005 show. The initial lineup featured V6 and V8 engines with rear-wheel drive, and for the first time on a Lexus sedan, the option of all-wheel drive with the V6-powered GS 300 and GS 350 models. The GS 450h performance hybrid joined the lineup in 2006.

The production GS was built on a newly designed mid-size platform which would also be used on the second-generation IS. Production of the third generation began on 24 January 2005 in the city of Tahara, Aichi, in Japan, where all GS models would be built. The third generation GS was also the first model to feature Lexus' own L-finesse styling upon its introduction.

In October 2003, Lexus premiered the LF-S (Lexus Future Sedan), a concept car which presaged the design characteristics of the upcoming GS. The design features on the LF-S concept included a slingshot cabin, sleek profile, and fastback rear deck lid, which were translated to the production GS, while the windshield cleansing system, glass roof, and side cameras were not.

In 1999, development commenced on a successor to the S160 under chief engineer, Shigetoshi Miyoshi. Styling for both the exterior and interior was done under lead designer Yasuhide Hosoda between 2000 and 2002, during which L-finesse came to fruition in 2001. By 2002, a design was finalized, to be introduced the following year.

The third generation GS was the introductory Lexus model for the marque's new L-finesse design philosophy. Characterized by swooping lines, a fastback profile, and more muscular styling, the GS indicated the future direction of the Lexus lineup. The production GS featured a slingshot cabin, first previewed on the earlier Lexus LF-S concept. The production GS also retained the quad headlamp design from the second generation model and previous Lexus SC while adding LED tailamps, and one-piece bumpers to create a more uniform appearance. The drag coefficient on the third generation GS design reached 0.27 C_d.

The GS interior was available with ash leather and black Bird's eye maple wood trim, cashmere leather and brown bird's-eye maple trim, or black leather and walnut trim. Major standard features included a water repellent front door glass, an acoustic windshield, solar energy absorbing glass, electrochromic auto-dimming side mirrors with puddle lamps, electrochromic auto-dimming rearview mirror, 10-way driver and front passenger power and heated seats with three-position Lexus Memory System, power tilt/telescoping steering wheel, and a power trunk closer. The GS sedans also were the first to feature the latest generation of Lexus' SmartAccess keyless system–-adding a push-button start for the first time as standard.

Other unique features included a driver-side hidden drop-down panel for infrequently used controls, a standard 7-inch touchscreen display in the center console, and LED lighting in the cabin. Unique to the Lexus GS series was a three-pod instrument cluster with machined aluminum facings and an electrochromic feature which adjusts for the amount of reflected sunlight to reduce glare. Optional features included a power moonroof, ventilated front seats with perforated leather, power rear sunshade, rain-sensing wipers, a discrete 5.1 surround sound 14-speaker 330 watt Mark Levinson premium sound system, XM-satellite radio and DVD-based navigation with backup camera and Bluetooth technology.

The third generation Lexus GS came standard with dual front airbags, front driver and passenger knee airbags, front and rear row side curtain airbags, and front row side torso airbags standard while rear row side torso airbags were optional. An Adaptive Front-lighting System (AFS) was standard on the V8 model while optional on the V6 model. The radar-based Pre-Collision System (PCS) with a Dynamic Radar Cruise Control system was optional. PCS can automatically apply up to 0.3g of deceleration if the driver does not react to imminent crash warnings. Anti-lock braking, electronic brakeforce distribution, brake assist and Vehicle Stability Control (VSC) are standard on all models. VSC with the electric power steering system can immediately alter steering torque assist during evasive maneuvers.