Ana Pelaez shot a course-record nine-under-par 63 on moving day at the Comunidad de Madrid Ladies Open to take a three-shot lead into the final round at Jarama-RACE Golf Club in the Spanish capital.
The 24-year-old from Malaga, playing in her first Ladies European Tour tournament as a rookie professional, fired nine birdies for a 54-hole total of 17-under-par.
Agathe Sauzon from France shot a seven-under-par 65 to stay in touch, three strokes adrift, while Spanish amateur Cayetana Fernandez, 17, carded a five-under-par 68 and occupies solo third place on 13 under.
Down woman Olivia Mehaffey posted her second 69 in three days to move to seven-under-par and a share of 17th place.
It would have been even better but for just her second bogey on the par-four 18th.
"It was a great day out there today. It was also my mother's birthday and I didn’t have a present for her, so I guess this round works for her," leader Pelaez said.
"My putting was good. My shots into the greens were there. My brain was there. Everything was ideal."
She relied on an invitation to get into the tournament, due to having finished outside the top 80 at Q-School. A win would set up her career, but she didn’t show any sign of nerves: "I love pressure. I live for this. I cannot wait for tomorrow," she added.
"I just felt adrenaline; pure adrenaline. Sometimes it’s good, but I felt so much adrenaline I had to take a deep breath and be in the moment, but it was amazing. I hope that many more people come tomorrow and support us."
One stroke further back, Sweden’s Linn Grant shot 69 and lies in fourth place, a stroke ahead of Gabriella Then, from the United States.
Then, the LET Q-School winner, won her first title on the Epson Tour at the Garden City Charity Classic in Kansas last week. She shot an eight-under-par 64 which included six birdies and a hole-in-one at the 17th where she used a 7-iron from 162 yards downhill.
With a level par round of 72, the halfway leader Tiia Koivisto slipped back into a share of sixth place with Pia Babnik and Manon de Roey. The Race to Costa del Sol leader Maja Stark, Linnea Strom and Leonie Harm share ninth place on nine-under-par.