Green's unlikely triumph at Hazeltine National near Minneapolis was also her first LPGA Tour title and elevates her towards the elite of the female game.
In just her second LPGA Tour season and playing just her 36th LPGA Tour event as a cardholder, Green becomes the third Australian female golfer to win a major title along with Jan Stephenson and Karrie Webb, her win coming 13 years after the last by Webb at the then Kraft Nabisco Championship in 2006.
Needing a par at the last to hold off one of the game's most powerful players, Sung-Hyun Park, Green turned her 6-iron over into the left-hand greenside bunker but, especially given the circumstances, hit a superb bunker shot to 5 feet and holed that to win by one over the defending champion, Park.
There was a gap of two shots back to the third placed Mel Reid, Nelly Korda and Lizette Salas but all the honours go to Green who became the first-ever first-time LPGA Tour winner to win wire-to-wire.
Green’s composure had been exemplary all week, especially given what was at stake as she eyed not only the breakthrough victory on the LPGA Tour but the winner’s cheque of more than US$550,000.
Green began the day with a one-shot lead over Jutanugarn but it would not be the Thai golfer who would prove her biggest danger.
Park, the former world number one, began the day five shots behind Green and through nine holes that gap remained. Then would come a mid-round slump from Green when she dropped three shots in four holes and with Park closing fast she needed all she could muster to stay in front.
Three pars got things back on track before an 18-foot birdie putt at the 16th gave Green a two-shot lead but the job was not yet done and when Park birdied the 18th from 15 feet the gap was just one and, playing in the group behind, a par at the dangerous last became just that much more of a challenge for the 22-year-old Green.
Green found the fairway from the tee but was some 180 yards from the hole. But when she eventually holed the putt for victory she was mobbed by her Australian golfing buddies and others who ran on to the green to congratulate the stunned but popular winner.
Immediately after her round, Green spoke with on-course commentator Jerry Foltz.
“I was really nervous playing the last five holes and I was really happy to make that clutch putt as the what was what I was struggling with through the middle of the round and to sneak that one on the last it really is surreal.”
“I didn’t feel too nervous the first few holes and was pretty happy with how I was hitting it but coming towards the back nine missing the putts on 8 and 9 really hurt and I wasn’t in the right head space for that but making the putt on 16 relieved everything.
“I knew Sung Hyun had made the birdie at the last and I really didn’t want to have to play that hole again.
“I’ve always wanted to win in front of an Aussie crowd and although this wasn’t in Australia that is what it felt like today,” added Green referring to the strong Australian contingent who followed her all day including its greatest female golfer Karrie Webb.
Minjee Lee, who most predicted would be the next Australian female to win a major title, finished 30th while last week's runner-up in Michigan, Su Oh, finished 56th.
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