Following his epic last-eight victory over Jannik Sinner on Thursday, Spaniard Alcaraz ended the fairytale run of America’s Frances Tiafoe in another thrilling five-setter in New York overnight.
The 19-year-old third seed recovered from dropping the first set on a tiebreak in an exhausting encounter to triumph 6-7 6-3 6-1 6-7 6-3.
It will mean a first Grand Slam final appearance for Alcaraz, who is the youngest male player to reach a major showpiece since compatriot Rafael Nadal 17 years ago.
“It’s amazing to be able to fight for big things,” said Alcaraz. “First time in a final of a Grand Slam. I can see the number one but at the same time it’s so far.
“I have one more to go against a player who plays incredible. I’m going to give everything that I have. I’m going to enjoy the moment and let’s see what happens.”
His opponent on Sunday will be fifth seed Ruud, who saw off the challenge of Russian Karen Khachanov in four sets, 7-6 6-2 5-7 6-2 at Arthur Ashe Stadium.
It is a second Grand Slam final appearance of the year for the 23-year-old Norwegian, who was bested by Nadal in straight sets in the French Open final at Roland Garros in June.
The winner of an intriguing showdown is guaranteed to become the new world No1 as well as claiming their first major title, replacing current incumbent Daniil Medvedev, who was dumped out in the last-16 by Nick Kyrgios.
“This was another great match from my side. I think we were both a bit nervous at the beginning. This match is probably the biggest match of both of our careers,” said Ruud after a contest with Khachanov that included a marathon 55-shot rally.
“Phenomenal in the second and the fourth sets and Karen stepped up in the third. I’m just extremely happy. I thought the French Open might have been the only slam final of my career. Here I am back again a couple of months later. It feels beyond words to describe.”