The defender has become the club's third high profile signing of the summer on the same afternoon Antonio Conte revealed Emanuele Giaccherini will join Sunderland.
The 25-year-old is one of the most highly-rated defenders in Italy and was linked with Premier League champion Manchester United before the Bianconeri firmed up their interest.
Ogbonna grew up in Turin and made his Torino debut against Calcio back in February 2007, before spending the following campaign on loan at Crotone.
Since then he has blossomed into one of the Granata's star men and has built a reputation as an athletically-blessed performer who can cover both the centerback and left back slots.
That versatility is sure to have swayed Juve boss Antonio Conte into securing his signature given his preference for a 5-3-2 formation.
Ogbonna made 10 appearances for Italy's under-21 side before progressing to the senior ranks and he was included in the Azzurri's Euro 2012 squad, though he did not feature in the tournament.
His arrival comes on the same afternoon it was revealed Emanuele Giaccherini will leave Juventus Stadium for Sunderland, as the Serie A champion looks to claw back some of its transfer outlay.
Strikers Fernando Llorente and Carlos Tevez have already joined the club in what has been a busy summer transfer window for the Bianconeri so far.