Just months after splitting from fiancée Caroline Wozniacki, the 25-year-old Ulsterman confirmed his status as the man most likely to dominate golf in the post Tiger Woods era.
In the months since he broke-off his engagement, McIlroy has won the British Open, the BMW, the Bridgestone WGC and now the USPGA, his fourth major.
A stunning and gritty back nine in a rain delayed final round saw McIlroy hold off Phil Mickelson, Rickie Fowler and Henrik Stenson to triumph at Valhalla.
After finishing on 16 under to beat Mickelson by one, the Irishman admitted to the BBC: “I gutted it out. It was different to my previous major wins.
“To win my second major this year and fourth by 25, it’s just incredible.
“Winning the Open was huge for me and I said I wanted to back it up.
“I didn’t think in my wildest dreams I would have a summer like this. I just played the best golf in my life.”
McIlroy has now equaled the number of majors won by Jack Nicklaus at the same age and is sure to set his sights on the American’s record total of 18.