The British 18-year-old became the first qualifier in history to win a grand slam and ranked No.150 in the world at the start of her tournament in New York some three weeks ago, she prevailed 6-4 6-3 against fellow debutant teenage finalist Fernandez.
Victory in the final caps a remarkable and life-changing couple of months for Raducanu, who also reached the Round of 16 of Wimbledon before pulling out of the competition because of medical reasons.
Raducanu is the youngest women's grand slam finalist since a 17-year-old Maria Sharapova took the title at Wimbledon in 2004 and she feels the women's game is in strong hands.
"First of all, I really want to congratulate Leylah and her team – she played some incredible tennis and has beaten some of the top players in the world," Raducanu said in her on-court interview as she was handed the trophy by the legendary Billie Jean King.
"The level was extremely high and I hope we play each other in many more tournaments and hopefully finals.
"It shows the future of women's tennis and depth of the game is so great, every player in the draw has a shot at winning any tournament.
"I hope the next generation can follow in the steps of some of the legends, for example Billie Jean right here."
Raducanu did not drop a set in her remarkable run at Flushing Meadows as she became the first British female to win a Major since Virginia Wade on home soil at Wimbledon 44 years ago.
Wade was in attendance for the final at Arthur Ashe Stadium – as was fellow Brit Tim Henman – and Raducanu will now be out to match or indeed better the success of the three-time grand slam winner Wade.
"It means so much to have Virginia here and also Tim , British icons and for me to follow in their footsteps... it gave me the belief I could do it."
Raducanu proved too strong for world number 73 Fernandez with a perfect mix of power and precision that saw her hit 22 winners to her opponent's 18.
Only twice did Fernandez break Raducanu and the British teenager won 67 per cent of points behind her first serve.
"Leylah is always going to play great tennis and fight, that is why she is in the final, I knew I would have to dig deep," Raducanu said.
"As for this three weeks in New York, I would say having such a supportive team, the LTA my agent, and everyone back home watching on TV, thank you so much for your support over the years.
"Thank you for making me feel so at home from my first qualifying match, you have spurred me on in some difficult moments and I hope me and Leylah put on a good match today."