|McIlroy became the second successive Northern Irishman to win the title after Graeme McDowell last year [EPA]
Rory McIlroy eased to an eight-shot victory at the US Open, signalling his rich promise as a potential golfing great by becoming the championship's youngest winner since 1923.
The 22-year-old Briton, eight strokes in front of the chasing pack overnight, carded a two-under-par 69 on a humid and overcast Sunday at Congressional Country Club to claim his first major title.
"I couldn't ask for much more and I'm so happy to be holding this trophy," McIlroy said at the trophy presentation. "I couldn't be happier."
Long regarded as a future world number one, McIlroy posted a tournament record total of 16-under 268, to leave his nearest challengers trailing in his wake and banish memories of his final-round Masters meltdown two months ago.
After safely parring the last where he two-putted from just off the front of the green, he clenched his right fist and pumped it in celebration as he broke into a smile.
Emerging Australian talent Jason Day fired a 68 to finish alone in second, two strokes better than South Korea's Yang Yong-eun (71), Britain's Lee Westwood (70) and Americans Kevin Chappell (66) and Robert Garrigus (70).
McIlroy eclipsed the previous best aggregate of 12-under set by Tiger Woods at the 2000 US Open and became the second successive Northern Irishman to win the title after Graeme McDowell last year.
"My hat's off to Rory this week," McDowell told reporters after closing with a 69.
"It's been waiting to happen. He's been this good for a long time, and it's great to see him fulfill his potential. He's an awesome player.
"Nothing this kid does ever surprises me. He's the best player I've ever seen. I didn't have a chance to play with Tiger when he was in his real pump, and this guy is the best I've ever seen, simple as that."
All eyes were on the record-breaking McIlroy when he teed off on Congressional's heavily tree-lined Blue Course on Sunday afternoon.
With his accurate long game, spectacular approach play and silky smooth putting, he had decimated the field over the first three days, setting tournament lows after 36 and 54 holes.
The only question remaining was how he would handle the mounting pressure and lofty expectations heaped upon him going into the final round.
Any concern was swiftly erased when McIlroy rolled in a nine-footer to birdie the opening hole and stretch his lead to nine.
He picked up another shot at the par-four fourth, where his approach pitched 15 feet beyond the cup before spinning back to within four feet.
He coolly sank a clutch par-saving putt from 15 feet at the fifth before reaching the turn in two-under 34 with an eight-stroke cushion.
A tap-in birdie at the tricky par-three 10th maintained McIlroy's lead, with Yang having also recorded a birdie there.
After bogeying the 12th where he found a bunker off the tee and failed to reach the green with his second shot, the Northern Irishman got back to 17 under with a birdie at the par-five 16th.
Though McIlroy three-putted for the only time this week to bogey the 17th, he safely parred the last to complete an unforgettable week.