New Zealand's Lydia Ko felt she had enjoyed a "Cinderella" story after ending an eight-year wait for a major title by winning the Women's Open Championship at St. Andrews on Sunday, just a fortnight after her Olympic gold medal triumph in Paris.

The New Zealander finished in champion style with a superb birdie on the 18th hole of a windswept Old Course to complete a round of three-under-par 69 as she claimed her third major title with an overall score of seven-under-par.

"It is surreal," Ko told Sky Sports. "Winning the gold medal in Paris a few weeks ago was almost too good to be true. Heading into the weekend I thought 'how is it possible for me to win the Open?' This is almost too good to be true. Out of all the major championships, this was the one I had the least amount of confidence in."

The victory gave Ko, 27, her first major title since the 2016 Chevron Championship (then known as the ANA Inspiration).

"It is the most Cinderella-like story these past two weeks. To be holding this trophy now, it is some achievement," said Ko, who as a 17-year-old became the youngest player to be ranked as world number one in professional golf.

"I thought to myself, because of the last few weeks, it is not going to happen. So don't overreact and play the shot in front of you. My two goals were to par the 11th and birdie the 18th. I achieved both. This is such a special place," she added.

"All my achievements are special, even the silver and bronze at the Olympics. I always said I wanted to win another major championship. Here I am now as a three-time major champion."

USA Ryder Cup captain Keegan Bradley pulled off a surprise win at the BMW Championship, with his final round of even-par 72 securing a one stroke victory on Sunday at Castle Pines.

Bradley had only qualified after claiming the final spot in the top 50 of the FedEx Cup standings with his last round at the St. Jude Championship last week.

The 38-year-old overnight leader drew on all his experience, however, to produce a solid round on the Colorado course and finish at 12-under-par for the tournament.

After coming into the week ranked 50 out of 50, Bradley has now surged up the FedEx Cup rankings and will head to next week's final event, the Tour Championship in Atlanta, sitting fourth in the standings.

Sweden's Ludvig Aberg, Australian Adam Scott and American Sam Burns had all threatened to steal the lead on the back nine, but Bradley, who made two birdies and two bogeys – including on the final hole when the win was in the bag – held firm.

It was the seventh win on the PGA Tour for Bradley and the victory was greeted with chants of 'USA, USA' around the 18th green for a player strongly associated with the country's Ryder Cup team.

Bradley and Scott had been jousting for the lead for most of the weekend and the outcome was still in play on the final green.

With Bradley enjoying a two-stroke advantage, Scott had a chance for birdie, while the American faced a long and tricky putt from off the green.

A birdie for the Australian and a bogey for Bradley would have sent their duel to a playoff, but after Scott missed his 18-foot attempt, Bradley could afford his bogey.

"I was shaking over that last putt. I was ready for those cheers. We did it. It was a battle all day," he said.

Bradley had described his performance last Sunday, to sneak into the top 50, as one of the most nerve-wracking experiences he had endured on the PGA Tour and smiled when considering how his week turned out.

"It just shows why you've got to grind it out every week, because you never know how fast it can switch. Now I go to Atlanta with a chance to win the FedExCup," he said. "I can't believe it. I'm so excited. My dad, first time he's seen me win, so we're pumped."

Bradley was watched by his father Mark, who taught him the sport while working as a club professional.

(With input from AFP)