Chun In-gee doubled her overnight advantage to lead the Evian Championship by four strokes from fellow South Korean Park Sung-hyun going into Sunday's final round.
Chun had led by two strokes after day two of the prestigious event, a major co-sanctioned by the LPGA Tour and Ladies European Tour since 2013.
And she reached 19 under on the leaderboard in Evian-les-Bains on Saturday courtesy of a six-under third round of 65.
A double bogey at the par-five ninth was Chun's only blemish on moving day in France, as she holed six birdies and an eagle three at 15.
It was all Park could do to try and keep pace with her compatriot, managing a bogey-free four-under 67 to remain outright second.
China's Shanshan Feng is third at 13 under, pursued by Ryu So-yeon (12 under) and Kim In-kyung, who carded the low round of the day, a seven-under 64, to sit outright fifth on 10 under.
The defending champion, world number one Lydia Ko of New Zealand, is tied 36th on even par for the tournament after an error-strewn third round of 75.