Rose Zhang beat Jennifer Kupcho with a par at the second playoff hole to win the Mizuho Americas Open in her professional debut on Sunday, a rare feat in LPGA history.

The 20-year-old American, who was the world number one amateur for 141 weeks, is the first player to win an LPGA title while making her pro debut since Beverly Hanson did it in 1951.

"What is happening? I just can't believe it," Zhang said after two-putting for par at the second playoff hole, the 18th at Liberty National in Jersey City, New Jersey.

"It was just last week when I won NCAAs with my teammates," said the player who won her second straight US collegiate title in her last amateur hurrah. "To turn pro and come out here, it's just amazing."

Zhang, who also won the Augusta National Women's Amateur this year, started with a two-stroke lead, but on another cold and blustery day she couldn't find a birdie, although she made a string of clutch par putts on the way to a two-over par 74 for a nine-under total of 279.

Kupcho was in the clubhouse on 279 after a three-under 69 when Zhang arrived at the 72nd hole with a one-shot lead, having just made testing par-saving putt at 17.

Zhang was in the left fairway bunker off the tee and couldn't get her par-saving putt to drop and she and Kupcho headed back to the 18th tee for the playoff.

After both scrambled for par at the first playoff hole, both found the fairway at the second. Zhang put her approach within eight feet of the pin while Kupcho's second shot got hung up at the front of the green some 60 feet away.

Kupcho putted past and off the green and Zhang had the luxury of two-putting for the win.

"This golf course is rough," Zhang said of a layout that didn't yield a bogey-free round on Sunday. "I really got a bit of everything, got a taste of the pressure, got a taste of the wind and I tried to stay composed, as always.

"I know that golf was just a grind and you really have to dig deep. Once again, that's what I did."

The victory gives Zhang the immediate option of LPGA Tour membership. She had made 13 starts on the tour as an amateur, including in eight major championships, with her best finish a tie for 11th at the 2020 Chevron Championship.

After her bogey at the par-three fourth, Zhang reeled off 12 straight pars, missing a short birdie putt at 16 that would have given her a two-shot cushion.

South Korea's Ryu Hae-ran finished third after a 70 for 280, with Japan's Ayaka Furue, South Korea's Ji Eun-hee and India's Aditi Ashok sharing fourth on 281.