Pettersen finished with a 21-under 267 to beat former world No. 1 Davies, with Paula Creamer a further three strokes back in third.

Pettersen went into the last round with a seven-stroke lead but 44-year-old Davies chased impressively to put pressure on the leader.

On the 17th green, Pettersen's three-foot par putt struck the pin and curled out to leave her with a bogey, while Davies knocked home a five-foot birdie putt to level the scores.

On the final hole, Pettersen hit a three-iron from 225 yards to within 15 feet of the hole and then rolled home the eagle putt.

Davies almost matched her, but the English player could not sink her 25-foot eagle attempt, leaving a tap-in for birdie.

"To make that last putt, that was the best putt of my life," Pettersen said. "I was just like, "Drop! Drop! Drop! Please drop!"

"I probably hit my best shot of the day on my second shot (on the 18th) and I just told my caddy 'I just really want to make this putt'."

Pettersen and all players struggled on a day that combined a heavy downpour with strong winds and high humidity.

"Laura was close, but what a match," Pettersen said.

"Today I was struggling, not playing my best and just kept fighting and hanging in there and trying to take chances when I got them.

"That last putt was the best in a long, long time."

After shooting a 71 in the first round, Davies rekindled memories of her prior dominance of the women's tour by shooting 66, 66, and 65 over the final three rounds.

"I played well this week, I putted well and I've driven it magnificently," Davies said.

"She made a great shot on the last and that was it. It was all about that one shot.

"I had a really good putt, I thought I made it."

It was Pettersen's fifth title of the year, and she collected a $195,000 winner's check.

Creamer carded a 66 in the final round to finish two strokes ahead of Australia's Rachel Hetherington.