Mitchell, who was called up to the squad only after injury ruled out Jack van Poortvliet, starts at scrum-half in what looks like a move by coach Steve Borthwick to inject some pace and urgency into England's attack after their dire warm-up campaign.
He has six caps but this will be only his second start.
May, another late addition after Anthony Watson's injury, starts at right wing, with Elliot Daly on the left in the team announced on Thursday.
Curry, one of the stars of England’s run to the final four years ago, returns at openside flanker having overcome a series of injuries.
Veteran scrum-half Danny Care is on the bench and in line for his second appearance in a World Cup having played in the dead rubber against Uruguay in 2015.
He made his international debut in 2008 but missed the 2011 tournament through injury after being named in the squad and was overlooked by Eddie Jones in 2019.
Owen Farrell's suspension opens the way for George Ford at fly-half, with Manu Tuilagi and Joe Marchant in the centres.
Courtney Lawes will captain the team from blindside flanker while fellow international centurion Dan Cole is a surprise starter at tighthead prop, brought in for his scrummaging expertise.
In the absence of the suspended Billy Vunipola, the only specialist number eight in the squad, Ben Earls packs down at the back of the scrum.
Marcus Smith is among the replacements, covering the fly-half and full-back positions despite never starting a professional game at 15.
'STERN TEST'
"With an excellent week of preparation in Le Touquet, the players are now looking forward to starting their Rugby World Cup campaign under the lights in Marseille on Saturday,” said Borthwick, who arrived with his squad in a roasting hot Marseille on Thursday afternoon.
"After a number of impressive performances in the last 12 months by Argentina, we know that the first game in our pool will provide a stern test."
Borthwick will hope the return of Curry, one of the game's best defenders and a real danger at the breakdown, will help stiffen a defence that missed 27 tackles in the 30-22 Twickenham defeat by Fiji that completed a miserable World Cup warm-up series.
Curry picked up a hamstring injury in the Premiership final in May, then injured his other hamstring and then an ankle to keep him on the sidelines throughout Borthwick’s uninspired start after taking over from Eddie Jones.
England have lost six of their nine tests under Borthwick, beating only Italy and Wales (twice), and have been leaking three tries a game while really struggling to score any, particularly through their backs.
Curry did play against Argentina in last November’s 30-29 defeat that ended a run of 10 straight victories in the fixture for England, who have also won the teams' three World Cup clashes - all in the pool phase.
This is the first time, however, that the Pumas (sixth) have gone into a match ranked above England (eighth).
England team:
15. Freddie Steward, 14. Jonny May, 13. Joe Marchant, 12. Manu Tuilagi, 11. Elliot Daly, 10. George Ford, 9. Alex Mitchell; 1. Ellis Genge, 2. Jamie George, 3. Dan Cole, 4. Maro Itoje, 5. Ollie Chessum, 6. Courtney Lawes (captain), 7. Tom Curry, 8. Ben Earl
Replacements:
16. Theo Dan, 17. Joe Marler, 18. Will Stuart, 19. George Martin, 20. Lewis Ludlam, 21. Danny Care, 22. Marcus Smith, 23. Ollie Lawrence