As part of Cadillacs pattern for abandoning names in favor of three-letter codes, STS replaced the Seville nameplate as the brands the mid-range sedan representative for the 2005 model year. Using the Cadillac design language showcased on the CTS and SRX, the STS was a premium sedan with a strong emphasis on performance. Unlike its predecessor, the Cadillac STS was introduced with a standard rear-wheel drive layout or an optional all-wheel drivetrain.
Two engines choices were presented on the 2005 STS consisting of a 255-horsepower 3.6-liter V-6 or a 320-horsepower 4.6-liter Northstar V-8. Both Cadillac engines shared the benefits of variable valve timing and were paired with five-speed automatic transmissions. Standard conveniences found on the 2005 Cadillac STS included leather seating, dual-zone climate control, ultrasonic rear parking assist and OnStar. Front, side and curtain airbags, traction control, StabiliTrak as well as anti-lock disc braking was provided as safety protection. RainSense windshield wiper, Memory package, 15-speaker surround sound system and HID headlamps were optional equipment on the Cadillac STS.
Available with an optional equipment group package on the V-8 model, Magnetic Ride Control provides quick-reacting handling characteristics. In 2006, the high-performance Cadillac STS-V model was added to the line-up. The transmission of the STS was upgraded to a six-speed gearbox for the 2007 model year while the 2008 Cadillac sedan included a new 302-horsepower, direct-injected 3.6-liter V-6 engine. 2008 also introduced the Platinum trim level consisting of 18-inch chrome wheels, semi-aniline leather interior and additional chrome accents. The V-8 engine was dropped from the Cadillac STS during the luxury vehicles final year of production in 2011. In 2012, the XTS replaced both the STS and the DTS.