The 60-year-old had only joined Chelsea last year but negotiations via agent Fali Ramadani, the same man who ensured he was released from his Napoli contract, ensured an early end to his time in England.
There are no details on how much compensation Juve are paying for this release, as Italian sources put it at £1.1m and English papers at £5m.
Sarri will replace Max Allegri, the boss who narrowly pipped him and Napoli to the Scudetto in 2018.
Despite winning the Europa League, reaching the Carabao Cup Final and taking Chelsea to third place in the Premier League, Sarri was still criticized by some sections of the fanbase and media.
He leaves the Stamford Bridge side with a more than respectable tally of 40 wins, 11 draws and 12 defeats, having scored 123 goals and conceded 67.
“In talks we had following the Europa League final, Maurizio made it clear how strongly he desired to return to his native country, explaining that his reasons for wanting to return to work in Italy were significant,” said Chelsea director Marina Granovskaia.
“He also believed it important to be nearer his family, and for the well-being of his elderly parents he felt he needed to live closer to them at this point.”
It will be an interesting season in Turin as Juventus as spending big because they want to win the Champions League now. But Sarri is a coach who believes in the process and repetition. Can the two co-exist. This demand for instant gratification versus a manager who is better in year two than year one?