Gran Turismo 4 (often abbrieviated as GT4) is a racing video game for Sony PlayStation 2 which is published by Polyphony Digital. It was released on December 28, 2004 in Japan and Hong Kong, February 22, 2005 in North America, and March 9, 2005 in Europe, and has since been re-issued under Sony's 'Greatest Hits' line. Gran Turismo 4 is one of only four titles for the PlayStation 2 that is capable of 1080i output, one of them being Tourist Trophy which was also created by Polyphony Digital.
GT4 was delayed for over a year by Polyphony Digital, and had its online mode removed (later added as a stand-alone online test version) during development. GT4 features over 700 cars from 80 manufacturers, from as early as the 1886 Daimler Motor Carriage and as far into the future as concepts for 2022. The game also features 51 tracks, many of which are new or modified versions of previous original courses, with some notable real-world additions, such as the Suzuka Circuit, or Le Mans Circuit de la Sarthe.
The Chinese, Japanese and Korean versions of the game were bundled with a 212-page driving guide and lessons on the physics of racing. A limited edition, Gran Turismo 4 Online, was released in Japan in the summer of 2006. A PSP enhanced port entitled Gran Turismo Mobile was originally planned, but was later dropped and replaced by a new project, Gran Turismo (PSP), which was released October 1, 2009.