The 24-year-old came into the final day of the major a shot behind Louis Oosthuizen, but a run of three straight birdies on the back nine helped propel the American past the South African, who had topped the leaderboard over the tournament’s previous three days.
In his first appearance at the British major, Morikawa became the first man to win both the PGA Championship and the Open on his debut at the tournaments.
Just over two years ago, Morikawa was ranked 1,039th in the world having finished tied for 14th at the RBC Canadian Open in June 2019. Now he is a two-time major winner.
Heading into the final day of action, it was almost impossible to pick a winner between Oosthuizen, Morikawa and Spieth.
Despite having a shot advantage, Oosthuizen has developed an unfortunate habit of failing at the last hurdle over recent years. And so it proved, with two bogeys on the front nine dropping the South African down the leaderboard.
Morikawa pounced to take advantage, coming up with three straight birdies to close out the back nine that gave him a four-shot lead before moments later, a birdie from Spieth reduced the gap to three.
It was never plane sailing for the American.
If overnight leader Oosthuizen faded over the final 18 holes, three-time major winner Spieth looked back to his best as he made a run at the top of the leaderboard.
The 27-year-old American’s putter was red hot and his chipping clever as he recovered from some early set backs to put some pressure on Morikawa.
Oosthuizen did produce one moment of magic, hitting the flag on the tough par-three 11th hole, just millimeters from a memorable hole-in-one.
Meanwhile, reigning US Open champion Rahm was putting together his own push for the coveted Claret Jug.
An eagle on the 7th hole and a run of four straight birdies on the back nine shot him up the leaderboard and had the 26-year-old Spaniard dreaming of a second successive major.
But Morikawa was unfazed. Despite his youthfulness and relative lack of experience at majors — he’s only played in seven before this weekend — Morikawa calmly saw off his rivals.
He kept his driving accurate, his iron shots precise and his putting crisp as he dealt with every challenge the tricky Royal St George’s course could offer.
And under the blinding English sun as the UK experienced a mini-heatwave, Morikawa was able to tap home the historic putt on the 18th hole to be crowned the 149th Open champion.
The American is the first player to win the Open on his debut since Ben Curtis in 2003 at Royal St. George’s.
More to follow