It was a victory that required blood, sweat and in the end a few tears as the 18-year-old became the first qualifier to win a Grand Slam title and the first British woman to hoist a major trophy since Virginia Wade, who was watching from courtside, triumphed at Wimbledon in 1977.
Wade has been in New York cheering from courtside seats while an infatuated Britain gathered around televisions and held its collective breath on Saturday as the teenager played out a Hollywood ending on an improbable script.
'An absolute dream'
Raducanu's win received the royal stamp of approval with Queen Elizabeth taking to Twitter to offer congratulations along with other members of the royal family.
"It's an absolute dream," beamed Raducanu, who will shoot up from 150th to number 23 in the world rankings on Monday. "I've always dreamed of winning a Grand Slam. You just say these things.
"You say, I want to win a Grand Slam. But to have the belief I did, and actually executing, winning a Grand Slam, I can't believe it."
The first Grand Slam final - men's or women's - to be contested by two unseeded players was an unfathomable match-up featuring qualifier Raducanu and little-known Fernandez, who was 73rd in the standings going into the tournament.
One unseeded player making a major final would be considered remarkable - two enters the realm of unbelievable.
All the more remarkable was that Raducanu's march to the title required 10 matches and she did not drop a single set or even play a tie-break, swatting aside more experienced opponents with the same ease as she hammered winners.
Fernandez and her journey at US Open
Fernandez left a graveyard of seeds and champions in her trail to the final, her victims including second-seeded Aryna Sabalenka, four-time Grand Slam winner and defending champion Naomi Osaka, fifth seed Elina Svitolina and three-time Grand Slam winner Angelique Kerber.
Despite what the statistics might say, Raducanu insisted that winning the U.S. Open was not a easy as it might have looked.
"I'd say even though I didn't on paper drop a set, I think I faced a lot of adversity in every single one of my matches," she said. "I can pick moments where I was down.
"Just to come through those are important.
"I think what I did very well this tournament was press in the moments that I really needed to."
'I can't believe I am here'
For the first time during the Flushing Meadows fortnight, the 19-year-old Canadian faced a younger opponent, if only by a couple of months. But she had no answers for the icy cool Raducanu.
Both players walked onto a frothing Arthur Ashe Stadium court with "I can't believe I am here" ear-to-ear grins but soon had their game faces on, focusing on the challenge ahead.
The charismatic teens had charmed the New York crowds with fearless play and contagious enthusiasm, leaving excited fans a difficult choice over who to back in the final, which in the end was evenly split.
"It was an incredibly difficult match but I thought the level was extremely high,” said Raducanu.
“Leylah’s always going to play great tennis and always going to fight – that’s just the competitor she is... I think just staying in the moment, focusing on what I had to do... really helped in those tough times.”