Lydia Ko secured a late birthday present when she birdied the second extra hole to beat American Morgan Pressel in a playoff at the Swinging Skirts LPGA Classic in California.
Two days after turning 18, the South Korean-born Kiwi successfully defended her title and picked up a seventh LPGA victory in the process.
Pressel, however, will be ruing the birthday gifts she offered Ko by squandering two chances for victory.
The American missed a 15-foot birdie putt at the final regulation hole, the par-five 18th, and also missed from inside 10 feet at the first extra hole.
"It's been a great birthday week again," Ko told the Golf Channel. "This week I hit the ball really well and it definitely makes this course a lot easier."
Eight years ago, Pressel became the youngest player to win a major at the age of 18 but she has only triumphed once since and remains without a victory since 2008.
Ko showed why she is worthy of her world number one ranking when she sank a clutch eight-foot birdie at the 18th to force extra holes, after earlier sinking a 40-footer at the 15th that took a sharp right-hand turn and dropped in on the final roll.
The New Zealander carded a two-under 70 and Pressel shot a 72 with the pair finishing on eight-under 280, one ahead of the long-time leader Brooke Henderson, the Canadian teenager dropping back with a final round of 74.