Raducanu, the 18-year-old Briton, the first qualifier to reach a Grand Slam final, will attempt to become the first British woman to win a Grand Slam title since Virginia Wade in Wimbledon in 1977.
He has not lost a single set to reach the final at Arthur Ashe Stadium.
Fernandez, a 19-year-old Canadian southpaw ranked 73rd in the world, has beaten defending champion Naomi Osaka, Aryna second seeded Sabalenka and fifth seed Elina Svitolina on her way to the final.
“It’s going to be a tough match for sure. He’s playing great tennis,” Raducanu said.
“But I think I’m also playing very good tennis. I’m excited to get out.”
It’s the first time teens have faced each other in a Grand Slam final since he was 17 years old. Serena Williams defeat Martina Hingis, 18, at the 1999 US Open.
One will walk away with her first Grand Slam trophy on the same court where Williams, a 23-Slam winner about to turn 40, took her first trophy 22 years ago.
“There is no limit to my potential, to what I can do,” Fernandez said.
“Every day we have to keep working hard, we have to keep going. Nothing is impossible. I’m happy that now everything is going well.”
If she succeeds, Raducanu, who is ranked 150th, would become the first British woman to win the US Open since Wade in 1968.
She is the youngest Slam finalist since the age of 17. Maria Sharapova won at Wimbledon in 2004.
“I wasn’t really sure what my game was going to be like,” Raducanu said.
“My level of tennis has surprised me by the way I managed to face some of the best players in the world.
“I knew I had some kind of level inside of me that was similar to these girls, but I didn’t know if I could hold it for a set or two. To be able to play against the best players in the world and beat them, I honestly can’t believe it.”
Fernandez said: “I believed in my game, but it has also helped me open my eyes that I can win against these great players.
“I am happy to have this experience and to see where my tennis level is.”
Raducanu’s unexpected arrival in the final has created great excitement in the British media, hungry for success in tennis since Andy Murray’s career went into decline.
“Greatness awaits Raducanu in a showdown that heralds a brilliant and exciting generation,” was The Times headline on Saturday.
Both Fernández and Raducanu have created a real-life fantasy that rivals any Disney story.
“One word that really stuck with me is ‘magic’ because not only is my career really good, but also the way I’m playing right now,” Fernandez said.
“I’m having fun. I’m trying to produce something for the crowd to enjoy. I’m glad that whatever I’m doing on the court, the fans love it and so do I.
“We will say that it is magical.”
The pair first met in events under the age of 12.
“Since then, we have both come a long way in our games and as people,” Raducanu said.
“I’m sure it will be very different from the last time we met. But we are both playing good tennis, so it will be a good match.”
Raducanu and Fernández have been successful early in their careers, but Sabalenka warned after Fernández beat her that there is a difficult road ahead, as demonstrated by the mental health struggles that have beset Osaka.
“The question is when will you start to understand what’s going on and where you are, how well can you deal with all these expectations and this level, all this pressure,” Sabalenka said.