Japan's Chie Arimura shot a 1-under 71 for a one-stroke lead over Australia's Karrie Webb after the third round of the HSBC Women's Champions in Singapore on Saturday.
Arimura had two birdies and one bogey for an 11-under 205 going into the final round.
Webb shot a 70.
Arimura could have had a bigger lead, but she missed short putts on the 15th and 16th holes.
She had a three-shot lead with two holes to play, but three-putted on the 17th and made par on the final hole.
Webb birdied the 18th.
Arimura, who has never won an LPGA tournament, will be paired Sunday with Webb and top-ranked Yani Tseng of Taiwan.
Tseng had a 69 and trails by six strokes.
"I might be nervous," Arimura said. "Just competing against those great players is even hard for me to believe.
"Even now, it's like a dream."
Webb has won 36 LPGA titles, more than any other active player.
"I feel pretty fortunate to only be one shot behind," the 36-year-old Webb said. "I've got a great opportunity to win."
Tseng, who is seeking her fourth title of the year, is tied at 5 under with South Koreans Na Yeon Choi (71) and Sun Young Yoo (73).
Morgan Pressel of the United States followed with a 70. Mika Miyazato (70), Cristie Kerr (73) and Ai Miyazato (70) trail by nine strokes.
Tseng earned the top ranking after winning the Australian Women's Open and Australian Ladies Masters on the Ladies European Tour in February and last week's LPGA Thailand event.
"It's a big gap," she said. "But this is golf.
"You never know until the last putt drops."
South Korea's I.K. Kim had the best round of the day with a 67.
She trails the leader by seven strokes.
Michelle Wie and Juli Inkster finished with 77s, well off the pace.