The 20-year-old Shibuno, a rookie on the Japan LPGA Tour who was playing for the first time outside of her country, birdied five of the final nine holes in a four-under 68 to finish at 18-under 270.

"I was also thinking about if I were to make this putt, how I was going to celebrate," Shibuno said of approaching the 18th.

"Eat a lot of sweets."

Salas, who started the final round tied for fourth, quickly played herself into contention with three birdies in the first four holes, and she added five more in a seven-under 65.

Jin Young Ko, who was seeking her third major title of the year, was two shots back in third after a bogey-free 66.

Morgan Pressel (67) finished fourth at 15 under with second-round leader Ashleigh Buhai (70) alone in fifth a shot further back.

The best Australian was World No.4 Minjee Lee, who carded a final round 69 to finish in a share of 11th at eight under while compatriot Hannah Green shot a final round 69 to finish a shot further back.

RIGHT: Lee was the best of the Australians, finishing T11th. PHOTO: Richard Heathcote/Getty Images.

Su Oh carded an error-free 66 in her last round to finish 12 shots off the pace while fellow Australian Sarah Kemp struggled to a 78 to end up seven over par.

Largely unknown before the championship, Shibuno – nicknamed "Smiling Cinderella" – started Sunday with a two-stroke lead but lost it with a double bogey on the par-4 3rd.

She bounced back with birdies on Nos.5 and 7 before a bogey on the 8th at Woburn Golf Club.

But in three of four rounds, Shibuno has shone on the back nine. She closed with just 31 shots on Sunday – and just 30 on Thursday and Saturday.

"Now that I've won, I think a lot of the Japanese people will know me, but in actuality, I just wanted to live a quiet life," Shibuno said.

"I was looking online and I did see that it's been 42 years since a Japanese player has last won.

"I do feel that I have accomplished something great but I really don't know the reason why I was able to accomplish it."