The England and Wales Cricket Board (ECB) confirmed the appointments following the dismissal of Brendon McCullum as Test coach earlier this month after a series of disappointing results and off-field issues. McCullum, however, will continue as England's white-ball coach.
Fleming, 53, takes charge of a national team for the first time in his coaching career.
The former New Zealand skipper has enjoyed remarkable success with Chennai Super Kings, guiding the franchise to a record five Indian Premier League titles during his 17-year tenure.
"I'm incredibly excited. It's one of the most prestigious coaching positions in world cricket, and I'm honoured to be appointed," Fleming said.
Fleming will not be in charge for England's upcoming Test series against Pakistan, which begins on August 19. Assistant coach Marcus Trescothick will serve as interim head coach before Fleming joins the squad later this year ahead of England's Test tour of South Africa.
Root, 35, will begin his second stint as England's Test captain after previously leading the side between 2017 and 2022, during which he registered a national-record 27 Test victories in 65 matches.
Root welcomed the appointment, describing the opportunity to work alongside Fleming as "a huge motivator."
"He has proved over a long period that he is an exceptional leader with great knowledge of the game. I'm looking forward to working with him and helping build a winning environment," Root said.
