Webb did not drop a shot and picked up six birdies during a fabulously consistent round which took her to 15 under par.

She finished two shots clear of fellow Australian Michelle Ellis and Spain's Paula Marti, who shot 68 and 69 respectively.

Webb completed a career Grand Slam of the four Majors at last year's McDonald's LPGA Championship.

And she now becomes the first player to win the five different major titles available in her career as the British Open replaced the Du Maurier Classic as the fourth major last year.

"With it being an LPGA major now, it's just that bit more special," said Webb.

"I'm delighted the way I stood up to the pressure at the weekend. This is definitely one of my greatest moments.

"I really enjoyed playing at Turnberry. To win here on such a great golf course, where so many great players have won, is a dream come true."

Webb, who missed the cut at the US Open last month, had trailed overnight leaders Carin Koch and Jennifer Rosales by three shots after the third round.

But she took the lead with four birdies in the first 10 holes and added two more at the 12th and 17th.

Ellis completed a great day for Australia with her best-ever finish in just her second professional season.

"It's awesome to shoot 68 and finish second. This is the first time I've put it together under the gun," she said.

Marti's reward is almost certain selection for Europe's team to defend the Solheim Cup in Minnesota next month.

"That's something I have been aiming for all year and this just feels so good," she said.

A clutch of players finished on 11 under, including Korea's Jeong Jang, Candie Kung, Catrin Nilsmark and overnight leader Jennifer Rosales.

Earlier Sweden's Asa Gottmo had hit an amazing albatross at the par-five seventh, but she finished with a disappointing 76.

Kathryn Marshall and fellow Scot Catriona Matthew were the best-placed British competitors on one-over-par 289, 16 shots behind Webb.