McIlroy left the course in North Carolina without congratulating his rival or attending the trophy presentation after coming second at a major for the fourth time since 2014.
Rory McIlroy has said he will “take a few weeks away” from golf after describing his final-round heartbreak at the US Open as his “toughest day” as a professional in the sport.
The 35-year-old finished second at a major on Sunday for the fourth time since winning the PGA Championship in 2014.
The Northern Irish golfer had been due to make an immediate return to PGA Tour action at the Travelers Championship starting in Connecticut on 20 June but his withdrawal was confirmed on Monday.
McIlroy had led the US Open by two shots at one point before he bogeyed three of his final four holes at the Pinehurst No.2 resort in North Carolina.
A bogey is when a golfer takes one more shot to complete a hole than the par listed for it – with the par setting out how many shots the hole should take.
Watching from the scoring room, McIlroy witnessed his US rival Bryson DeChambeau produce a remarkable 55-yard pitch from the sand to the green on the 18th hole.
He then converted the putt to clinch the US Open title.
McIlroy was pictured with his hands on his hips before making a quick exit from the resort without congratulating DeChambeau, speaking to the media or attending the trophy presentation.
The defeat meant McIlroy missed out on winning his fifth major and his first in 10 years.
In a statement shared on X on Monday, McIlroy said: “Yesterday was a tough day, probably the toughest I’ve had in my nearly 17 years as a golfer.
“Firstly, I’d like to congratulate Bryson. He is a worthy champion and exactly what professional golf needs right now. I think we can all agree on that.
“As I reflect on my week, I’ll rue a few things over the course of the tournament, mostly the two missed putts on 16 and 18 on the final day. But, as I always try to do, I’ll look at the positives of the week that far outweigh the negatives.”
Read more from Sky News:
People smuggler ‘at peace’ with dying on job
Justin Timberlake arrested for ‘driving while intoxicated’
Hopes a simple blood test could detect Parkinson’s
McIlroy added he feels “closer to winning my next major championship than I ever have”, adding he has shown his “resilience over and over again in the last 17 years and I will again”.
He continued: “I’m going to take a few weeks away from the game to process everything and build myself back up for my defence of the Genesis Scottish Open and The Open at Royal Troon. See you in Scotland.”
The Scottish Open begins on 11 July while The Open at Royal Troon begins a week later.
Shane Lowry, who finished 19th at the US Open, said: “From the outside looking in… this game is easy. But in reality it’s the worst game of all. We are very fortunate to get what we do from this game but over the last 24 hours it’s hit me.
“We do it for not only ourselves but for our family, friends and fans. What Rory has gone through is as tough as it gets in our game but I would like to encourage people if anything please be kind.”
Meanwhile, DeChambeau has been celebrating after pulling off one of the toughest shots in golf on the final hole.
“I still can’t believe that up-and-down,” DeChambeau, 30, said as he watched a replay from the video screen during the trophy presentation.
“Probably the best shot of my life.”