COQUITLAM - It was a day of improbable firsts on Sunday for Lydia Ko.

The 15-year-old became the youngest player ever to win an LPGA Tour event, as she bested a field that included 48 of the top 50 players on this year's money list to capture the CN Canadian Women's Open at Coquitlam's Vancouver Golf Club.

Ko entered play Sunday atop the leaderboard with a one-stroke advantage over Stacy Lewis, and fired a sizzling seven birdies - and just two bogeys - to solidify her final four-day tally of 13-under par 275.

"It's great to win, and the last few holes it got a bit nerve-wracking, but Stacy Lewis after my birdie on 15, she said, 'you know you can do it,'" Ko told reporters after her historic win. "It feels amazing _ It's always awesome to be able to play with the pros."

Ko is the first amateur since JoAnne Carner in 1969 to win a LPGA Tour event and the first amateur in tournament history to win Canada's National Women's Open Championship title. Having left her native South Korea for New Zealand about 10 years ago, Ko also claimed the Marlene Stewart Streit low amateur medal as the tournament's top amateur.

At 15 years, four months and two days, Ko becomes the youngest winner in LPGA Tour history, eclipsing the previous mark set by Lexi Thompson, who was 16 years, eight months and eight days when she won the 2011 Navistar LPGA Classic.

She also becomes only the fifth amateur in LPGA Tour history to win an official event and the first since Carner claimed the Burdine's Invitational in 1969.

As an amateur, Ko was unable to accept the $300,000 winners' cheque, which was awarded to Inbee Park as the second-place finisher.

Coquitlam's Jisoo Keel shot 77-78-155 to finish 11 over par, and missed the cut.