Which Gran Turismo title is listed as the first mass-produced game in the series with online multiplayer?

Gran Turismo 5 Prologue is listed as the first mass-produced Gran Turismo game to feature online multiplayer.

Released for the PlayStation 3 in 2007, Gran Turismo 5 Prologue functioned as a preview of the eventual Gran Turismo 5. Despite its “Prologue” status, it introduced a major series feature: online racing for up to 16 players at once.

The distinction matters because Gran Turismo 4 was intended to include online functionality, but that feature was removed before the final release. A test version existed, yet the finished mass-market game did not provide the same online multiplayer experience. Gran Turismo HD Concept also included an online time-trial feature, but it was a downloadable demo rather than the relevant mass-produced release.

Gran Turismo 5 later became the first mainline entry with online races, which can cause confusion when the series’ online history is summarized. The more precise answer is Gran Turismo 5 Prologue: it established online multiplayer in a commercially released Gran Turismo title before the full Gran Turismo 5 arrived in 2010.