Alexander Zverev recovered from two sets down to defeat Spain's Pablo Carreno Busta in a scrappy encounter and reach the US Open final on Friday.
The German fifth seed beat the 20th seed 3-6, 2-6, 6-3, 6-4, 6-3 in 3hr 23min inside Arthur Ashe Stadium to set up his first ever Grand Slam final.
He will play either second seed Dominic Thiem or third seed Daniil Medvedev in Sunday's showpiece.
It marked the first time in the 23-year-old Zverev's career that he came from two sets down to win.
"I actually looked at the scoreboard when I was down two sets to love," Zverev said.
"I was like, 'I can't believe it. I'm playing in a semi-final, I'm supposed to be the favorite and I have no chance, I'm playing that bad.
"So I knew I had to come up with better tennis and I knew that I had to be more stable."
Zverev made 36 unforced errors in the first two sets compared to just 12 for Carreno Busta as the nerves of the occasion seemed to get the better of him.
Double fault followed double fault and a string of misplaced, nervy forehands allowed Carreno Busta to build a sizable lead.
But Zverev began to seriously cut down on his mistakes in the third set, upping his service game and taking control of rallies with more powerful, accurate groundstrokes.
It continued to be a nervy, error-strewn affair, though, with both players appearing overwhelmed at times with coming so close to reaching their first tennis major final.
Zverev hit eight double faults overall to Carreno Busta's one. Zverev recorded 57 unforced errors to 44 for Carreno Busta.
But the tall German smashed way more winners, 71 to 37.
"I'm through to my first Grand Slam final and that's all that matters," Zverev said.
"I couldn't be happier, but there's still one more step to go for me," he added.
Zverev had reached his first Grand Slam semi-final at the Australian Open this year.
He now becomes the first German man to reach the final of a tennis major since Rainer Schuttler at the 2003 Australian Open.
This year's US Open field has been depleted by the absence of Roger Federer and Rafael Nadal.
The tournament was blown wide open by the disqualification of world number one and heavy favourite Novak Djokovic in the last 16 for hitting a line judge with the ball.
It means Sunday's final will see a first-time Grand Slam champion for the first time since Croatian Marin Cilic won at Flushing Meadows in 2014.
It also means there will be a Grand Slam champion other than Djokovic, Nadal or Federer for the first time since Switzerland's Stan Wawrinka won the third of his tennis majors at the US Open in 2016.