The Northern Irishman's 22-under 266 total matched the lowest in the history of the tournament, set by
The top-ranked McIlroy, whose win here in 2009 was his first as a professional, made just three birdies Sunday but kept mistakes off his card. His only bogey of the round came on the par-3 seventh hole at Emirates Golf Club's Majlis course.
"I just wanted to keep my ball in play and not really make any mistakes and try and pick off some birdies when I could on the par-fives," McIlroy said.
"I did what I needed to do. It wasn't the best round that I've played this year but I got the job done and that's the most important thing."
Sweden's Alexander Noren, making a comeback from a wrist injury which restricted him to playing just two events in 2014, had eight birdies in his round of 65 to take second place at 19-under 269.
"I never even thought of winning, Rory's playing so good," said Noren, who started the year ranked 654th.
Defending champion Gallacher closed with a 69 to give the Scot third place at 16-under 272.
There was a five-way tie for fourth on 15-under 273, involving Germany's
The $2.5 million tournament forms the closing leg of the three-stop Desert Swing of the European Tour.
With an eagle putt that looked as long as his golf journey around the world, Brooks Koepka surged into the lead and stayed there Sunday with a five-under 66 to capture the
Lingering for most of the final round, Koepka holed a 50-foot eagle putt from the fringe on the 15th hole and didn't make any mistakes the rest of the way.
The victory ended a long, arduous road for the 24-year-old from Florida. With no status in America, Koepka played the Challenge Tour in faraway lands like Kazakhstan and Kenya, winning four times to earn his European Tour card and then validating his status as a rising star by winning the Turkish Open last year.
But winning at home brought the strongest validation.
“It feels amazing,” Koepka said after his one-shot win over Hideki Matsuyama,
Of the five players who had a share of the lead in a wild final hour at the TPC Scottsdale, Matsuyama had the last chance to catch Koepka until his 18-foot birdie putt on the final hole missed well to the right.
Palmer shared the lead with a birdie on the 15th, but he had to settle for pars the rest of the way for a 66. So did Watson, who reached the front of the 17th green only to three-putt from just over 100 feet and made par. He closed with a 65.
Matsuyama, who holed out from 129 yards for eagle on the first hole and was the first player to catch up to Laird, took the lead with a beautiful pitch behind the green on the par-five 13th. He went 44 consecutive holes without a bogey until Matsuyama three-putted on the 14th hole, and he never recovered. He shot 67.
Koepka already was eligible for the Masters with his tie for fourth at the
This was his second victory in his last four starts, both against strong fields.
Koepka had not played since the Nedbank Challenge in South Africa two months ago, taking a full month off away from his clubs and working hard over the last few weeks after a change to his putting stroke.