It was a victory that required blood, sweat and in the end a few tears as the 18-year-old became the first British woman to hoist a major trophy since Virginia Wade, who was watching from courtside, won 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.
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," said Raducanu, who will shoot up from 150th to No 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.
Raducanu did not drop a single set or even play a tie-break in her 10 matches at Flushing Meadows, swatting aside more experienced opponents with the same ease as she hammered winners.
Fernandez's giant-killing run to reach the final saw her claim victories over second-seed Aryna Sabalenka, four-time Grand Slam winner and defending champion Naomi Osaka, fifth seed Elina Svitolina and three-time Grand Slam winner Angelique Kerber.
"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," Raducanu 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."
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 Fernandez had no answers for the icy cool Raducanu.
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, but the North American connection saw Fernandez enjoy most of the support, particularly when she trailed.
"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.”
While the scoreline might hint at a one-sided affair, the near two-hour contest featured plenty of jaw-dropping tennis and more than a dash of drama, particularly in a second set that Raducanu threatened to run away with when, at 5-2 up, she earned two match points on Fernandez's serve.
The battling Canadian mounted a comeback to stay alive and when the Briton went down chasing a ball and scraped her knee - leaving blood dripping down her leg - the tide looked ready to turn.
As trainers bandaged the wound, Fernandez, who had just earned a break point, looked on in frustration, not wanting to lose the building momentum.
In the end, however, nothing was going to prevent Raducanu from realising her destiny, as she returned to finish off her opponent with an ace.
"I have no idea what I'm doing tomorrow," said Raducanu, who might indulge in a New York shopping spree after pocketing a winner's purse of $2.5 million, almost 10 times her previous career earnings of $303,000. "I'm just really trying to embrace the moment, really take it all in.
"Right now, no care in the world, I'm just loving life."