Updated

Lydia Ko won the U.S. Women's Amateur on Sunday, beating Jaye Marie Green 3 and 1 in the 36-hole final at The Country Club.

Ko, the South Korean-born New Zealander who tops the world amateur rankings, won at 15 years, 3 months, 18 days to become the second-youngest winner in tournament history. Kimberly Kim was 14 years, 11 months, 21 days when she won the 2006 tournament. Ko won the New South Wales Open in January in Australia at 14 to become the youngest player to win a professional tour event.

"I've won a medal at each of the three USGA tournaments I played in (this summer), so it's pretty good," said Ko, who also earned medals as the low amateur in the U.S. Women's Open and for reaching the semifinals in the U.S. Girls' Junior.

The 18-year-old Green is from Boca Raton, Fla.

"Oh my gosh, I don't want this day to end," Green said. "I've never had that people be so supportive. Lydia has such a great attitude, in that she laughs at everything and she's fun to play with."

Ko took a 1-up lead to the lunch break, and has 4-up after 26 holes.

Inspired by her most recent successes in amateur golf, she is in no hurry to turn pro.

"I want to go to college, so turning professional isn't a priority," she said. "There are so many things to learn as an amateur."