BREAKING NEWS: Stokes appointed England Test captain
Root led his country in the longest format for just over five years, but brought his long reign to an end this month following an abysmal run of just one win in 17 matches.
Stokes has agreed to step up from his role as vice-captain after holding talks with new managing director of men's cricket Rob Key.
The England and Wales Cricket Board (ECB) approved the appointment of Stokes on Tuesday after Key recommended the 30-year-old for the job.
All-rounder Stokes said: "I am honoured to be given the chance to lead the England Test team. This is a real privilege, and I'm excited about getting started this summer.
"I want to thank Joe for everything he has done for English cricket and for always being a great ambassador for the sport all across the world.
"He has been a massive part of my development as a leader in the dressing room, and he will continue to be a key ally for me in this role."
Key, who started his role this month with plenty of issues to address, said: "I had no hesitation in offering the role of Test captain to Ben.
"He epitomises the mentality and approach we want to take this team forward into the next era of red-ball cricket. I am delighted that he has accepted, and he is ready for the added responsibility and the honour. He thoroughly deserves the opportunity."
Stokes' first match as skipper will be when a series against New Zealand starts at Lord's on June 2.
England should also have appointed a new Test head coach by the time they face the Black Caps after Chris Silverwood was sacked in the wake of a 4-0 Ashes hammering in Australia.
The ECB has opted to appoint separate head coaches for the Test and limited-overs teams.
Gary Kirsten, Simon Katich, Tom Moody and Graham Ford are among the names to be linked with the Test job.