The 18-year-old completed her surreal run in New York with a 6-4 6-3 win over her 19-year-old Canadian opponent in a thrilling final.
Playing in just her second Grand Slam tournament, Raducanu won all 20 sets on her way to the trophy, becoming the first qualifier in the Open era to win a Slam.
The crowd were treated to a tense finish in the Arthur Ashe Stadium. Raducanu served for the match at 5-3, but cut her leg as she went break point down, leading to a medical time-out and a clearly irritated Fernandez.
However, the British tennis player shrugged off the delay, saving a further breakpoint before closing out her third championship point with an ace.
At a glance: 5 key points
- Emma Raducanu became the British woman since Virigina Wade in 1977 to win a major trophy.
- Raducanu became the youngest Briton to win a Grand Slam title, and the youngest woman to win a Slam since 17-year-old Maria Sharapova at Wimbledon in 2004.
- The 18-year-old started 2021 ranked No 345 in the world. Her victory in New York raises her to No 23. And the new British No 1.
- Raducanu was also the first woman to win the US Open without dropping a set since Serena Williams in 2014.
- Raducanu was sitting her A-Levels little more than three months ago having not played a competitive match for more than a year. She will take home £1.8m in prize money.
What’s been said?
Speaking to former British number one Tim Henman on Amazon Prime, Emma Raducanu said: "It means everything to hold this trophy and I don’t want to let go right now.
"Yesterday there were weird feelings I couldn’t put my finger on - I think that’s just normal. When I came out it was business as usual, one point at a time.
"I had to fight hard for that first set and keep myself ahead in the second. In the key moments, I came out with some clutch serves."
"I’ve always dreamed of winning a Grand Slam. You just say these things. But to have the belief I did, and actually winning, I can’t believe it," she said.
"I first started when I was a little girl, but I think the biggest thing that you have visions of is the winning moment, and going to celebrate with your team, trying to find your way up to the box.
"That’s been playing in my head, like, a couple of nights. I’ve fallen asleep to that.
"For me, I don’t feel absolutely any pressure. I’m still only 18 and I’m just having a free swing at anything that comes my way," she said.
"That’s how I faced every match here in the States. Yeah, it got me this trophy, so I don’t think I should change anything."
Layla Fernandez, who turned 19 on Monday, became a fan favourite thanks to some epic battles on the Arthur Ashe Stadium court.
She beat the defending champion Naomi Osaka, 2016 winner Angelique Kerber and second seed Aryna Sabalenka on her run to the final
Speaking to the crowd in her post match interview, Fernandez said: "Today is going to be hard but Emma played amazing. Congratulations," she said.
"I am very proud of myself and having the crowd has been amazing. Thank you so much New York. Thank you everyone."
After answering questions, Fernandez asked for the microphone to deliver a message to the New York crowd on the 20th anniversary of the September 11 terror attacks.
She praised the city’s toughness, saying: "I hope I can be as strong and resilient as New York has been the last 20 years. I love you, New York and hope to see you next year."
Neither Fernandez nor Raducanu were born when the attacks occurred, and Fernandez asked her parents on the morning of the match about their memories of the day.
"Obviously I don’t know much about what really happened, but with the few information that I do have, I know that New York has suffered a lot the past years," she said.
"Just having them [New Yorkers] here happy, lively, just going back to the way they were, having my back during these tough moments, has made me stronger and believe in myself."