Salas looked likely to win her maiden Major, especially when she hit it to 5ft on the 18th but her putt just lipped out on the right edge.
She must have thought that a playoff was on the cards before Shibuno rolled in an 18 footer for the title.
Last week’s Evian Championship winner and World Number One Jin Young Ko was looking to win her third Major of the season but came up two shy to finish 3rd after a 66.
“I was looking at the board all the time and I knew my position,” Shibuno said of her putt on 18.
“I was also thinking how I would celebrate,” she said, revealing she would “eat a lot of sweets.”
Shibuno has won twice already on the Japan LPGA Tour this year and ranked 46th in the world before the week.
Woburn’s own Charley Hull was the top Brit at five under and in T24th.
It could have been much better for Hull but a four over par 76 on Sunday dropped her down the leaderboard.
Bronte Law was tied with Hull at nine under after three rounds but a 78 (+6) dropped her down to T35th alongside defending champion Georgia Hall.
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