Shibuno, nicknamed "Smiling Cinderella", is looking to become only the second Japanese golfer to win a women's major after Chako Higuchi won the KPMG Women's PGA Championship in 1977.
"I hit so many good shots on that front side".
The Japanese holed an 18-foot putt on the final hole to secure victory in style and end Salas' hopes of taking it to a play-off.
Hinako Shibuno hadn't played a golf tournament outside of Japan before this week.
Park Sung-hyun (68) of South Korea sits third on 11 under, while compatriot Ko Jin-young - already the victor of two majors this year - is ominously placed four off the pace after a 68 lifted her into a tie for fourth with Morgan Pressel (66) and Lizette Salas (70). The two players combined to shoot eight under on the final nine holes, which were particularly kind to Shibuno-she shot even par on the front nine over the four days and 18 under on the back. "I felt like I was going to cry on the 18th but the tears didn't come out".
"I'm trying not to keep thinking it's a major", she said.
"I had a little pressure, but I like that pressure", world number one Ko said. "I'm really happy I didn't hook any shots".
She said her only goal this week was to make the cut - but now she can dream of becoming a Major champion.
Playing outside Japan for the first time as well as in her first major, Shibuno reacted with glee and astonishment, covering her mouth with her hand after the winning putt rattled in at Woburn for a closing four-under-par 68.
One shot further back from Salas is a group of five including Celine Boutier of France, Caroline Masson of Germany, Sung Hyung Park of South Korea and two English girls, Bronte Law and local favourite Charley Hull.
"I have so many people out here supporting me and I am pleased I could play well for them".
Tournament organisers had feared the lack of a British challenger, after Law, Hull and defending champion Georgia Hall had each fallen back, would cause enthusiasm for the tournament to dwindle among spectators on the Marquess Course at Woburn.
Eighteen-year-old amateur Yuka Yasuda is at 3-under, followed by Minami Katsu and Ayako Uehara at 2-under.
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