Eunjung Yi fired a 10-under third-round score of 61 to power into the lead at the LPGA Tour Jamie Farr Owens Corning Classic on Saturday.
The South Korean started the day tied for seventh, three strokes adrift of overnight leaders Laura Diaz and Sarah Kemp, but produced the best round of the day to establish a four-shot lead.
Another South Korean, Song-Hee Kim, fired a seven-under 64 to earn a share of second place alongside American Morgan Pressel, third overnight, who shot 67.
Diaz had a nightmare day, failing to capitalise on her strong position with a three-over-par round of 74 and ended the day tied for 24th, while Kemp was in a seven-way tie for fourth.
Michelle Wie finished the day tied for 22nd after a one-under round of 70.