Conte signed a three-year contract before becoming Chelsea head coach in July 2016, after leading Italy at Euro 2016.
Antonio Conte's time as Chelsea manager looks like it could be nearing an end following reports he has been sacked.
Conte won the Premier League in 2016/17 and the FA Cup the following season, but Chelsea's title defence in 2017/18 was dismal and the Blues ultimately finished fifth.
"I am very happy to be coming to Chelsea and the Premier League", Sarri said in a statement.
Conte thanked his players, staff and the Blues fans, adding: "It was fantastic for me to be able to share my emotions, passion and enthusiasm throughout two unforgettable seasons with these awesome Chelsea supporters, who will always stay in my heart".
Conte produced a record 30 Premier League wins during his maiden season, which has since been thwarted by Manchester City's 32 victories last season, while he now boasts Chelsea's longest consecutive league wins with 13.More news: Sanchez misses start of United's U.S. tour over visa problem
Winning trophies didn't save Conte being shown the Stamford Bridge exit door as he was dismissed after guiding Chelsea to the FA Cup in May.
The Blues will be looking to mount a serious title challenge next term under Sarri following their disappointing campaign under Conte.
Sarri, 59, led Napoli to two second-place and one third-place finish in three seasons in charge.
"I am absolutely ecstatic to be here at Chelsea", he told the club's website. Maurizio's Napoli side played some of the most exciting football in Europe, impressing with their attacking approach and dynamism, and his coaching methods significantly improved the players at his disposal.
Chelsea finally put an end to Conte's two-year reign on Friday.