Victoria Azarenka pulled off an incredible fightback to beat Serena Williams in three sets and reach the US Open final.
Williams had stormed into the lead inside the first half an hour on court, looking unbeatable as Azarenka struggled to cope with her power.
But the Belarusian found her rhythm in the second set, breaking Williams to force a deciding set with the tide very much running with her.
The 38-year-old American then suffered a damaging injury to her ankle and despite vowing to play on, Azarenka held a clear physical advantage to seal a 1-6, 6-3, 6-3 victory at Arthur Ashe Stadium.
Azarenka, a two-time runner-up at Flushing Meadows, will face 2018 winner Naomi Osaka in Saturday's final.
The very fact that Azarenka had reached the last four was a testament to her phenomenal character after taking a hiatus from the game while she was pregnant with her first child.
Indeed, it was her first Grand Slam semi-final since 2013. As a stark contrast, Williams had been involved in 16 semi-finals in Majors during that time, winning eight titles in the process.
There was a higher motivation too for Williams as she chased a record-equalling 24th Slam, the record set by Margaret Court, and was only two matches away from achieving history.
The six-time winner stormed into a double break inside the first quarter of an hour of play, leading 4-0 as Azarenka really struggled to land her first serve and could only watched her second serve get gobbled up by a fired up Williams.
Having dropped only one game against Elise Mertens in the previous round, Azarenka's frustration was palpable and the difference in power between the two players played a major part as Williams wrapped up the first set 6-1.
Azarenka's body language changed from resigned to revitalised in the second set, however, and she began to make inroads on Williams' serve.
A rare lapse in the American's concentration would cost her dearly as Azarenka took full advantage of her first break points, whipping a backhand winner into the corner and the tide turned almost instantly.
Make no mistake, this was some of the finest tennis played by two women over the past years at a Grand Slam tournament. It was an endless exhibition of baseline rallies, corner to corner battles and stunning winners to finish off those points.
But it was Azarenka who found another level in the end, sealing the second set 6-3 with 12 winners and remarkably just one unforced error in the entire set.
A match of this quality deserved a dramatic finale and it was the fourth consecutive match Williams had been taken to a third set.
As the match began to become more tense, the margins for victory became smaller and even tougher for Williams, who required a medical timeout after aggravating an ankle problem.
It proved a hindrance for Williams, who was broken on her serve immediately after the injury and Azarenka never looked back, clinching the third set 6-3 to edge this instant classic.
