Rory McIlroy had no answer to a stunning late-birdie blitz from Collin Morikawa, who won the DP World Tour Championship and the Race to Dubai in the process on Sunday.
Morikawa birdied five of his last seven holes to shoot a 66 and secure a three-shot victory over Alexander Bjork and Matt Fitzpatrick.
It was bitter disappointment for McIlroy after rounds of 65, 70 and 67 saw him hold a one-stroke lead heading into the final round.
Looking for his second win in as many starts, McIlroy started slowly but a birdie on the tenth hole had him two shots clear of the field.
With many of his closest competitors faltering, including Shane Lowry who double-bogeyed the ninth hole, McIlroy looked in control of the tournament.
But a cruel piece of luck turned events on its head on the short par-four 15th hole.
McIlroy only had a pitch to the green for his second after a booming drive, but his pitch hit the flag halfway up and ricocheted back into the front bunker.
The Holywood man was unable to get up and down from the bunker, which coincided with Morikawa holding a long putt for birdie on the par-three 17th hole.
Now behind the American, McIlroy was pressing for birdies but ended up three-putting the 16th. With that his race was run, and he ended up bogeying the last to sign for a final round 74 and a share of sixth place.
Morikawa, 24, found the par-five 18th in two shots to set up a closing birdie which saw him bag the €2.64m tournament prize and a further €440,000 for winning the Race to Dubai.
“It’s really special,” said the two-time major winner, who only turned professional in June 2019. “It’s an honour to be the first American to win the Race to Dubai and to put my name on there with so many greats.
“Two years ago it wasn’t in my thoughts. It was, yeah, let’s go play around the world, but we didn’t know what the cards were going to be dealt.
“To have this chance and close it out, and not just closing it out with a top 10 or something, but to actually win the DP World Tour Championship, which concluded the Race to Dubai, what a great way to finish.”
Shane Lowry had to settle for share of ninth place finish after a closing level-par round of 72.