Ciganda carded a five-under 66 to sit 11 under overall, two clear German Caroline Masson, the first and second-round lead who was two under on Saturday, and Inbee Park, who shot a 67.
Ciganda is aiming to become the fourth Spanish player to win an LPGA Tour event and she told www.lpga.com: "It would be unbelievable. It would be a dream. I mean winning is always great, but I just want to try to focus on each shot...have a great round and then at the end if someone plays better, just congratulate [her]."
England's Jodi Ewart Shadoff and Becky Morgan of Wales both fell to level par and a share of 47th.