The Australian world number 114 led the tournament throughout and held her nerve on the final day to claim a shock victory.

Twenty-two-year-old Green had never before won an event on the Ladies' PGA tour but is now in the record books as a major champion.

Her level par final round of 72 was enough for glory as she ended the tournament on nine-under with a one-shot advantage over South Korea's reigning champion Park Sung-hyun.

Green bagged birdies at the second and seventh holes but three bogeys at the ninth, 11th and 12th gave hope to her rivals.

A superb 15-foot birdie putt at the 16th changed the momentum, however, before she crucially recovered to save par at the last after finding the bunker.

Park had birdied the 18th and was poised for a play-off but Green's up-and-down was perfect.

"I'm pretty much speechless," said Green, who joins Jan Stephenson and mentor Karrie Webb as Australian winners of women's majors.

"I was really nervous the last five holes and I made a clutch putt and that kind of got me through another one. 

"To make the one on the last really is surreal.

"Obviously I heard Sung made the last one, I knew I needed to make par. 

"I didn't want to play that hole again. 

"I'm really happy I made it.

"I've always wanted to win in front of an Aussie crowd and even though I'm not in Australia, it was like that today. 

"To win a major as my first event, I am over the moon."

Two-time major champion Jutanugarn was Green's nearest rival but her challenge in Minnesota fell off a cliff as she went round in a five-over-par 77 to end the tournament on three-under in a share of 10th place.

Park was five shots back after day three but her fine round of four-under propelled her up the leaderboard.

England's Mel Reid's superb round of six-under saw her gain a share of third-place with American Nelly Korda, three shots behind Green.