17-year-old Lydia Ko of New Zealand became the youngest golfer to hold top spot in the world rankings by tying for second place at the LPGA season-opening Coates Golf Championship in Ocala, Florida, on Saturday.
American Tiger Woods was previously the youngest golfer to become world number one when he did it in 1997 at 21, while Shin Ji-yai held the women's record after reaching top spot in 2010 aged 22.
The Korean-born Ko, led by as many as four strokes in the final round but slipped behind after a double-bogey six at the 17th hole as she finished one shot behind winner and good friend Choi Na-yeon of South Korea, who fired a 68.
Still, it good enough to lift her ahead of Inbee Park of South Korea in the rankings.
"It's amazing," said Ko, who also ended the 2014 season by winning the CME Titleholders event in November and a $1 million prize for claiming the season-long points race.
Ko, who as a 15-year-old amateur in 2012 became the youngest ever winner on the tour, shot a one-under-par 71 for 15-under 273 to share second with American Jessica Korda and Jang Ha-na of South Korea at the Golden Ocala Golf and Equestrian Club.
The precocious Ko began the final round with a one-stroke lead and was disappointed not to win the tournament, saying she hadn't thought about her ranking.
"I didn't really know what I needed to do to get in that position. All I was focused on was trying to play my best out here," she said. "So it's a huge honour to be in that ranking. I'm just going to just focus on my golf, not think about the rankings. The rankings always comes after the results."