World No.1 Johnson withstood a fierce early challenge from Smith to close with a four-under-par 68 to finish as a five-stroke winner over the Queenslander and South Korean Sungjae Im, who both closed with steely 69s.

The American's winning total was the equal-lowest under-par score in major championship history.

"I don't even know what to say. I'm so excited, it's hard to even talk," Johnson said.

"As a kid, you dream of playing in the Masters, and dream about putting on a green jacket.

"Since I played my first Masters, it's been the tournament I wanted to win the most. I was nervous all day, but I felt like I controlled myself very well.

"I proved that I can get it done on Sunday with the lead at a major.

"Especially in tough conditions and I proved to myself that I do have it, because I'm sure a lot of y'all think there was doubts in my mind, just because I'm in this position a lot of times.

"I've had the lead a couple times and haven't been able to finish it off, and so it is very nice to have a lead and then play well on Sunday and get the win. I couldn't be more happy."

The 36-year-old has been a dominant force in golf for some time, without validating his standing, winning at least one PGA Tour event in every season since getting his Tour card in 2008.

But it had often been suggested a resume of 23 PGA Tour wins, one major and a FedEx Cup title were not enough reward for his prodigious talent.

"Since I played my first Masters, it's been the tournament I wanted to win the most. I was nervous all day, but I felt like I controlled myself very well." – Dustin Johnson

But this victory has cemented his place amongst the all-time greats as a Masters champion forever more.

He is the first World No.1 to win the Masters since Woods did so in 2002 and smashed the tournament scoring record of 18 under held jointly by Woods (1997) and Jordan Spieth (2015).

He joined Australian Jason Day and Sweden's Henrik Stenson as the only players to post 20 under in a major.

Johnson's 24th PGA Tour win also takes him into a tie for 26th on the all-time win list with South African legend and three-time Masters champion Gary Player.

Johnson has threatened to win a green jacket for years, having finished in the top 10 in his past four attempts before his victory, including being runner-up to Tiger Woods last year.

This is also Johnson's 20th top-10 finish in majors with two wins and four runner-ups.

Next up for the 36-year-old is further domination. All things being equal, the next major will be his title defence in April.

"I'm not going to dial anything back," Johnson said.

"I feel really good about everything that I'm doing. I feel really confident in the golf game.

"My goal is to play for eight, nine, maybe 10 years, and then hang out with my kids and (partner) Paulina.

"So, until then, I'm going to work my butt off to be as good as I can."

Johnson received his green jacket from defending champion Tiger Woods, who pumped three balls into Rae's Creek for a 10 on the par-3 12th hole, his single highest score in his storied career.

Woods finished up one under and tied 38th.

The Masters was postponed to November from its usual April timeslot due to the COVID-19 pandemic and was played without patrons.

Only a few members of Augusta National, volunteers, media and officials plus close family and friends were there to witness history.

- Ben Everill, Australian Associated Press