On the course at Brookline Country Club, site of the historic 1999 Ryder Cup, the 33-year-old former world No. despite a bogey on the 18th and final hole.
"Even if I'm a little frustrated by this bogey, it's still a good start," reacted McIlroy, winner of the Canada Open last Sunday for the second consecutive year, after long months without a notable victory, and returned to 3rd place in the world rankings on Monday.
McIlroy's last Major dates back to 2014, during the PGA Championship.
No player has won the US Open since 1934, having won the previous Sunday on the professional circuit.
Several other players did nearly as well as McIlroy on Thursday, including Americans Hayden Buckley, Brian Harman, Aaron Wise and Matthew NeSmith (68), US Open defending champion Jon Rahm of Spain and the winner of the last British Open, Collin Morikawa (69).
Other players, who left later, were likely to do better than the Northern Irishman, who has been in good shape for a few weeks.
© 2022 AFP