It was a three-hour epic match under the lights on Arthur Ashe Stadium, and Wozniacki emerged triumphant to reach the quarter-finals of the US Open.
Wozniacki lost a first set she should have won but then fought back brilliantly from 4-1 down in the second set to move through to a last-eight clash with 10th seed Andrea Petkovic.
The Dane has received a lot of flak for her grand slam performances since becoming world number one almost a year ago but this might just prove to be a watershed moment.
Wozniacki looked the favourite for most of the first set, playing with greater pace and attacking intent than in her previous matches and making her opponent fight extremely hard for every game.
Kuznetsova is a supremely talented player, though, who arguably should have won more grand slam titles than just the US Open in 2004 and the French Open five years later.
She broke to serve for the set only to be broken straight back to love, setting up a huge tie-break for both players.
Wozniacki looked fired up and, helped by two serves below 65mph from her opponent, raced into a 5-2 lead. But back roared Kuznetsova, raising her game just at the right moment to win four points in a row.
Although she missed the first set point, Wozniacki threw in a very untimely double fault and on the second Kuznetsova took it when the top seed missed a forehand.
The Russian, a superb mover, generates more power on her groundstrokes than Wozniacki and she broke immediately at the start of the second set.
But one thing the 21-year-old does not lack is fighting spirit and Kuznetsova, a point from a 5-2 lead at one stage, was instead pegged back to 4-3.
That blow affected the 15th seed badly and Wozniacki made it four games in a row to move to the brink of taking the set, even bringing up a set point, but, in this tightest of battles, it seemed inevitable Kuznetsova would respond.
She did, breaking to level things again at 5-5, but the world number one gave herself a second chance. The quality continued to ratchet up, Kuznetsova saving a second set point with a stunning backhand winner, but on the third her resistance was broken.
That excited Wozniacki's boyfriend Rory McIlroy, who wrote on Twitter: "Come on!!!!!!"
The 21-year-old, who still looked remarkably fresh, was the clear favourite now and she reeled off nine points in a row at the start of the decider.
In the manner of what had gone before, it was not a quick ending, the top seed needing five match points to clinch victory, which she eventually did after three hours and two minutes.
Wozniacki was left to reflect on a very satisfying evening which should give her tremendous belief for what is a very tricky road ahead.
The Dane said: "It definitely gives you confidence to pull this match out. I felt like I played some good tennis out there. We had some unbelievable rallies at some points. I was moving very well.
"I think I handled the wind pretty well as well, so I'm just happy to be through to the quarter-finals. I could have been sitting here and been out already. But I'm very proud of what I've achieved today [Monday]."
For Kuznetsova, who made 78 unforced errors, there was a sense of deja vu after she also lost a tight match to eventual finalist Wozniacki at Flushing Meadows two years ago in the fourth round.
The Russian felt she paid for missing her chances, and she said: "I have not played a match so intense in a very, very long time. My US series wasn't so good. Finally I came here in good shape and was playing a good game.
"Yes, I did lots of unforced errors, but because I was trying to play very aggressive and to dictate, and I was doing this. She was a wall. To break a wall, you cannot hit hard. You have to mix it up.
"I think I did the right things. I just couldn't close it up in the right moments. This is it. She never gives the match away. I just didn't do the right things in certain moments when I had to."