The Mark X was introduced in November 2004 as a new line to succeed the Mark II, one of the best-selling lines of Toyota. The platform of the 12th-generation Crown (released in December 2003) was modified for the Mark X, significantly reducing the weight to improve the driving performance.

The wheelbase was 2,850 mm, the same as that of the 12th-generation Crown and 70 mm longer than that of the ninth-generation Mark II. The height was 25 mm lower than that of the Mark II. Its short front overhang was characteristic of the front-engine, rear-wheel-drive (FR) configuration, giving unique body proportions. The combination headlamps featured high/low beam lamps and a fog lamp in a linear layout, giving a sporty and dynamic feel to the front view. The exhaust outlets were integrated with the rear bumper and became flush with the body -- a design approach that was never before attempted in a Toyota sedan.

The drivetrain configuration was either FR or full-time 4-wheel-drive (4WD). The available power units included two V6 direct injection gasoline engines: the 3-liter 188 kW (256 PS) 3GR-FSE and the 2.5-liter 158 kW (215 PS) 4GR-FSE. The transmission was either a newly developed 6-speed automatic (for FR model) or a 5-speed automatic with quasi-manual gear shift features (for 4WD model). Also available was the function to automatically direct the low-beam headlamps to the direction the vehicle was being steered. The split-and-fold rear seats provided direct access to the trunk room, and the front seatbacks could be laid flat to form a bed together with the rear seat cushions.