The ex-Juventus and Italy coach's future had been under fierce speculation for months after he failed to follow up a Premier League-winning debut campaign with success in 2017-18.
Chelsea released their short, sharp statement on Friday morning that said: 'Chelsea Football Club and Antonio Conte have parted company.
Carlo Ancelotti replaced Sarri as Napoli coach following the end of the season, with a Chelsea move having been on the cards since Conte's relationship with the club's senior management turned sour in 2017-18. After his appointment in the summer of 2016, the Italian enjoyed a hugely successful first season in England, instilling belief in a damaged Chelsea side and leading them to the Premier League title.
The 46-year-old managed Empoli in the 2016/17 season but could not do enough to prevent the Italian minnows from succumbing to relegation from Serie A.
The Blues beat Manchester United in the FA Cup final at Wembley last season.
Chelsea are expected to announce Sarri's appointment on an initial two-year contract imminently - together with the signing of Italy global midfielder Jorginho for a combined fee of €65 million (£57.5m) - after convincing Napoli chairman Aurelio De Laurentiis to release the 59-year-old from his contract.
Napoli are also expecting compensation of around £4.5million for Sarri, who is under contract even though he is no longer their coach.
Chelsea legend Gianfranco Zola and Giovanni Martusciello are expected to join Sarri's backroom staff while Italian-Brazilian midfielder, Jorginho, is now undergoing a medical at Cobham and will also follow Sarri from Naples to London.
Zola scored 59 league goals for Chelsea across seven seasons between 1996 and 2003.
"I don't think Antonio helped himself, if I'm being honest, in the way that he came across at times", former Chelsea midfielder Dennis Wise told Sky Sports television.