DeChambeau made a scrambling par from a bunker at the last hole on Monday (AEST) after McIlroy missed a three-foot putt, blowing his chance.

LIV Golfer DeChambeau, who also won in 2020, finished at six under for the championship, one stroke ahead of McIlroy.

"I want to say Happy Fathers Day to all the dads out there," DeChambeau said.

"Unfortunately, my dad passed a couple of years ago and this one is for him.

"I can't believe that up and down on the last; that was probably the best shot of my life. That is huge to get up and down and win this prestigious championship - that will be the highlight of my life."

DeChambeau, who began the day with a three-shot lead, carded a final-round one-over-par 71 to become the second former Southern Methodist University golfer to win a US Open at Pinehurst No.2, with this title coming 25 years after Payne Stewart's memorable championship.

McIlroy's 69 was tainted by bogeys on three of the last four holes and he finished as US Open runner-up for the second year in a row. The 35-year-old, who won the title in 2011, was trying to secure his fifth major championship and first since 2014.

He drew even at six under with birdies on Nos. 9, 10 and 12 and, in the following group, DeChambeau bogeyed as the Northern Irishman jumped into the lead.

DeChambeau, 30, drove the green on the par-4 13th, but left an eagle putt short. It was tied again after McIlroy's tee shot at the par-3 15th was long and he failed to get up and down.

Tony Finau (67) and fellow American Patrick Cantlay (70) tied for third place at four-under, France's Matthieu Pavon (71) claimed fifth, one shot behind, while Japan's Hideki Matsuyama (70) was sixth at two under.

Only eight golfers finished under par for the week.

Min Woo Lee (71) was the best-placed Australian at five-over and joint-21st. Adam Scott (69) and Cameron Smith (72) both finished seven-over.

World No.1 Scottie Scheffler (72) tied for 41st place at eight-over. Just like the second round, he had no birdies in his final 18-hole tour around the course.

"I feel like I did some good things this week, but overall I definitely need to do some things better," he said.

- with PA and AAP