Nelly Korda's three-shot lead has disappeared at the Women's Open, leaving the world number one to start the final round two strokes behind Jiyai Shin.

Korda endured a back-nine collapse at the Old Course at St Andrews, recording a double bogey and three bogeys to finish the third round on 3-over-par 75.

She is 5-under for the tournament, sitting in third place behind Shin (7-under) and fellow American Lilia Vu (6-under).

Shin, a two-time Women's Open champion, demonstrated why she is a links maestro as she capitalised on Korda's struggles.

Despite two bogeys, Shin produced a 5-under 67 with the aid of seven birdies.

The 36-year-old South Korean, winner in 2008 and 2012, looks in the mood to make it three Women's Open triumphs after she tamed the infamous Road Hole 17th with a birdie.

Bidding for her seventh title this season, Korda said it was a "tough day".

She expected the final round would be played amid testing weather conditions.

"I think the winds are going to be high. There could be rain as well," Korda said.

"I'm going to keep a positive attitude. Take it one shot at a time. 

"I played really well the first two days, so I'm going to take that momentum into tomorrow."

Australia's Steph Kyriacou is part of an eight-way share of 19th position on even-par after posting a 72 in the third round.

Grace Kim, the only other Australian to make the cut, is tied for 70th place on 5-over.

Kim managed a 1-over 73 in the third round.

AAP/Reuters