Ryu So-yeon of South Korea smiles and waves at the crowd after sinking a birdie putt to tie for first on the 18th green during the fourth round of the US Women's Open golf tournament at The Broadmoor in Colorado Springs, Colorado, July 11, 2011. [Photo/Agencies]

COLORADO SPRINGS, Colorado - South Korea's Ryu So-yeon won her first major title by beating compatriot Seo Hee-kyung by three shots in a three-hole playoff for the weather-delayed US Women's Open on Monday.

The 21-year-old Ryu rolled in a five-foot birdie putt on the 18th green, the third extra hole, to complete her maiden LPGA victory before pumping her right fist in delight.

She was then soaked in champagne by fellow Korean players and former winners Pak Se-ri and Ji Eun-hee after they ran across the green to join her in joyful celebration at The Broadmoor.

"Unbelievable," a beaming Ryu said greenside, having become the third youngest US Women's Open champion after going par-birdie-birdie over the 16th, 17th and 18th holes in the playoff.

"I won KLPGA (Korean LPGA) tournaments six times but no majors and now I have won the US Women's Open. I can't believe it," she squealed in delight.

The orange-and-white clad Ryu, who plays most of her golf on her home circuit, became the fifth Korean to win the US Women's Open after her role model Pak (1998), Birdie Kim (2005), Park In-bee (2008) and Ji (2009).

Ryu So-yeon (L) of South Korea gets sprayed with champagne by Ji Eun-Hee (C) and Pak Jin-young (R) of South Korea after Ryu won the US Women's Open golf tournament at The Broadmoor in Colorado Springs, Colorado, July 11, 2011. [Photo/Agencies]

Only Pak, at 20, and In-bee, at 19, have won the coveted title at a younger age.

Ryu was especially delighted that Pak and Ji both stayed on at The Broadmoor's East Course to watch her secure victory on Monday after the year's third major had been heavily disrupted by rain, thunder and lightning over the previous four days.

"When I was a youngster, Se-ri was my hero," Ryu said. "Se-ri is (for) all the Korean golf players a hero.

"And Eun-hee, I practise with Eun-hee in Australia for winter training so I am really proud of it because my hero Seri Pak and Uni were fighting for me today so it's a really big power."

Ryu and Seo finished the regulation 72 holes at three-under 281, Seo having closed with a three-under-par 68 shortly before play was suspended because of darkness on Sunday evening.