England were opening the tournament at the Oval and reached a competitive, but getable, 311 from their 50 overs.
Jofra Archer put the Proteas in early trouble before Quinton de Kock settled things.
After the wicketkeeper fell though, England took control again but it was Stokes’ catch that caught the eye.
The all-rounder held onto a stunner on the boundary from Andile Phehlukwayo.
Running away from the ball, Stokes flew and reached out his right hand, somehow clinging onto the ball.
“I was in the wrong position to start with. I was supposed to be ten yards further in. If I had been it would probably have been a regulation catch but it was just one of those that sticks or it doesn’t,” said Stokes.
“I don’t practice being in the wrong position but we do train hard and try to practice those five per centers that do come along and that makes it a little bit easier when they do.
“The crowd’s reaction behind me was pretty awesome and I just tried to take it in as much as I possibly could. It does get you fizzed up when you are involved in something like that.
“It is a great feeling to look back at games and know you have contributed at crucial moments.
“There were a few nerves knocking around this morning – I haven’t felt like that for quite a long time – so after such a long build-up to the World Cup it is nice to walk away with a win.”
And though this is the first match of a six-week long tournament, fans think the catch of the tournament award is already sewn up.
One posted: “BEN STOKES HAS JUST PULLED OFF ONE OF THE GREATEST CATCHES YOU’LL EVER SEE! OH MY GOODNESS!”
Another added: “First match and we already gotta the catch of the tournament. Stokes, you bloody hell!”
While a third wrote: “Game 1 and catch of the World Cup already? Salute Ben Stokes!”
Another fan commented: “Catch of the tournament….Ben Stokes might turn out to be both—The Catch and the one who’s taken the beat catch.”
With a fifth adding: “Ben Stokes – Unbelievable catch! Will take some beating to go beyond that effort in this tournament.”
And another astonished fan wrote: “That was Freakingly Awesome!!! Ben Stokes has stunned himself!”
Stokes had earlier top-scored for England with 89 before starring in the field.
BBC TMS commentator Charles Dagnall added: “What a jaw dropping moment that was from Ben Stokes.
“That is a moment that will be clipped and replayed over and over and over.”