Park, the top-ranked woman in the world, was in the middle of a solid final round and still trailed by two strokes after the playing partners both had birdies at the par-5 10th on Sunday.
Everything changed in a two-hole stretch, when Park went ahead with consecutive pars. The 24-year-old South Korean went on to a bogey-free 4-under 67 that put her one stroke ahead of Ciganda, good enough for her third victory this season and fifth in her last 18 starts.
''She was hitting fairways and greens and making putts,'' said Park, who finished at 13 under. ''And I thought I played really great today, but I just missed a lot of birdie opportunities, so I thought this tournament might not be mine because I missed that many opportunities and Carlota was playing great golf. But she made a couple mistakes on the back nine.''
Ciganda's drive at the 416-yard 14th hole settled in the right rough with a tree between her and the green, and her shot from about 130 yards clipped a branch and came up short. She had a chance to save par but her 6-foot putt was short, and Park's par had her within a stroke of the lead.
After stepping away from her approach at No. 15, to a green surrounded by water on three sides, Ciganda hit a shot that went to the right and then rolled down into the water. Ciganda had to go back to a drop zone, where the 22-year-old Spaniard had a decent pitch before her first putt rolled over the left edge of the green for a double-bogey 6.
Park had another par and never trailed again.
''I'm very happy with my round and with my week. ... I had two bad holes on the back nine,'' Ciganda said.
With the $195,000 check for first place, Park exceeded $6 million in career earnings and will be No. 1 for the third week in a row. It was her sixth career LPGA victory, along with four more wins in Japan.
Ciganda played last season on the Ladies European Tour, where she was the top rookie and the top money winner – the first player since Laura Davies in 1985 to accomplish that feat. She won twice in Europe last year and now has her best LPGA finish.
At the 403-yard eighth hole, Park made a birdie before Ciganda followed with one of her own and responded with a slight fist pump when her ball dropped into the cup. They both had pars at No. 9, where Park was closer to the hole even though she had missed the green to the left, and they traded birdies again at the par-5 10th.
''I was happy and playing good and having fun and enjoying the day,'' said Ciganda, who had a closing 70. ''And then I think, let me see, the hole it bounced to the right, but I had a bogey there and then hit it to the water on 15.''
Caroline Masson had a 75 and finished eight shots back. The LPGA rookie from Germany led after each of the first two rounds and started the final round tied for second with Park.
Hee Young Park's 64 was the best round of the day on the 6,439-yard course with plenty of sloping fairways and raised greens.
Stacy Lewis, the Texas native and No. 2 player in the world, had a closing 66 when all six birdies and her only bogey came between Nos. 7-17. She tied for seventh for her sixth top-10 finish this season.
At the end of her round, Lewis signed the back brace of a 6-year-old Dallas girl who was diagnosed with scoliosis at 18 months old. Lewis wore a similar brace 18 hours a day for seven years after being diagnosed with scoliosis at age 11 and missed her first collegiate season after a spinal fusion.
Third-ranked Na Yeon Choi, among the four players tied for seventh, had 44 consecutive bogey-free holes and was 9 under before consecutive bogeys at Nos. 10-12. She went on to a 72.
Inbee Park sank a 4-foot birdie putt on the par-5 18th after Ciganda also birdied even after her final drive went into the right rough. But they had an unusual wait after hitting their drives, when Jee Young Lee, playing two groups ahead of them, had to replay the hole.
Before Lee signed her scorecard, officials determined she took an improper drop after her drive at No. 18 went out of bounds. Lee carded a 10 before Ciganda and Park got to play out the hole.
''It was all right. I mean it was actually really good, it ended up really good for me because I made a birdie,'' Park said of the delay. ''Maybe if I hit it in the water maybe I could have blamed it on them.''