After a bit of a wobble early on in the final round, the world No 1 turned the 84th Masters into a procession on the back nine at Augusta National.
The first top-ranked player to achieve the feat in this event since Tiger Woods in 2002, he won the rescheduled major by a resounding five shots, breaking all sorts of records in the process on a sun-kissed November afternoon in Georgia.
Johnson, who claimed a second major title as he added to his 2016 US Open success, became the first player in Masters history to get to 20-under-par on the back of a three straight birdies on the inward journey.
In closing with a 68 for a 20-under 268 total, the laid-back 36-year-old set a new winning aggregate for the event as he lowered the mark set by Tiger Woods (1997) and Jordan Spieth (2015) by two shots.
Australian Cameron Smith, who also earned a place in the record books as he became the first player to card four scores in the 60s in this event shared second spot with Korea's Sungae Kim, who was making his debut.
Former US PGA champion Justin Thomas was next on 12-under, one ahead of career grand slam-chasing Rory McIlroy and South African Dylan Frittelli.
With a four-shot overnight advantage, it was Johnson's event to lose, but, having failed to convert winning 54-hole positions in four previous majors, he started out following a 10-minute fog delay at the start of the day with a point to prove.
He'd hit every fairway in Saturday's second round, but, despite taking a 3-wood, his opening blow found sand on the right. He found the green from there, though, and started with a par-4.
After failing to find the short stuff again at the second, he then tried to be too cute with his third and plumped that in the front bunker. McIlroy had taken two to get out of there a bit earlier, but it was job done for Johnson as he produced a nice touch to set up a par save.
Up ahead, Smith birdied the second and third to cut the gap to just two before Johnson read the break to perfection as he rolled in 12-footer down the hill for his first gain of the day - a welcome nerve-settler - at the third.
He undid that, though, straight away with a sloppy three-putt at the fourth. That was just his third bogey of the week and first in 33 holes. As had been the case on the front nine in the second round, he followed one with another after finding sand off the tee at the fifth and having to take his medicine.
With Im having birdied the second and third, it meant his lead had been trimmed to just one shot - but not for long. A brilliant approach from Johnson set up a birdie from seven feet at the par-3 sixth, where Im dropped his first shot of the day.
The Korean also bogeyed the seventh after going long into a back bunker, but Smith had made a brilliant birdie there from behind the trees on the right of the fairway and the Australian was hanging in.
In a bit of trouble again after finding the pine straw with his drive at the ninth, his approach flirted with the bunkers on the left of the green and came down off the slope to around three feet.
Having bogeyed the fifth after missing the green on the left, that birdie took him out in three-under. But, after finding the heart of the green at the par-5 8th with two almighty blows, a birdie there left Johnson heading into the back nine with a two-shot lead.
That became three when Smith was unable to get up and down from the right at the 11th, something Johnson was able to achieve from a similar spot before ticking another box as he safely made the green at the treacherous 12.
It was probably just as well that he didn't know what had happened to defending champion Tiger Woods there an hour or so earlier in running up a 10. In signing for his par-3, Johnson had one arm in that Green Jacket.
The second one was already slipping in when he birdied the 13th to restore that four-shot advantage then added another one at the next. It was turning into a Masters-class from the American, who became the first player to reach 20-under in this event when he made it three in a row with a 4 at the 16th.
McIlroy, who had started the day eight behind following his costly 75 in the first round, had closed the gap to five after going out in three-under thanks to birdies at the third, sixth and eighth.
His slim chance of landing that piece piece of the majors jigsaw disappeared with an untimely bogey at the 11th, but, in backing up middle rounds of 66 and 67 with a closing 69, it was a good week's work by the four-time major winner.
"I played really well at the weekend and am pleased with my performance over the last three rounds," said McIlroy. "I felt a little more relaxed (this week) and I'm going to try and adopt this attitude and approach."
Bryson DeChambeau, the pre-tournament favourite, had an up-and-down final day. He was close to making an albatross-2 at the 13th, where he'd taken a 7 in the first round, but then dropped five shots in his last five holes.
He’d got himself checked for COVID-19 on Friday night after feeling dizzy and said: "It was unfortunate that some weird things happened to me this week that I could not forsee, but that's golf. At the end of the day, it is okay.”