Gran Turismo 4 Mobile is a racing video game under development exclusively for the PSP by Polyphony Digital. It is rumored to be a port of Gran Turismo 4 from the PlayStation 2 onto the PSP platform. Details regarding the game have been limited, and it is unknown if, or when, this game will be released.IGN: Gran Turismo 4 Mobile Canceled? (January 11, 2008)

Originally announced at the 2004 E3 Media & Business Summit Sony press conference, Gran Turismo 4 Mobile has been delayed numerous times and is currently not scheduled for release until 2009.

When first announced, Gran Turismo 4 Mobile was expected to be a flagship game for the PSP, and demonstrate the power of both the PSP and the UMD disc technology. Development of the next generation Gran Turismo games, including Gran Turismo 5 Prologue, required more resources than expected, resulting in the development of Gran Turismo 4 Mobile being postponed.Eurogamer: Yamauchi: GT PSP unlikely this year (April 4, 2008) The lack of updates from developers caused many to speculate that the game had been canceled.IGN: Gran Turismo 4 Mobile Canceled? (January 11, 2008)