The 18-year-old, who won Saturday's final in straight sets, was praised for her "poise and guts" during the historic match.
The teenager is the first qualifier to win a grand slam, and her victory comes just three months after she took her A-levels.
It led to praise from royalty, other sports stars and celebrities who were gripped by her remarkable and unprecedented success.
Following her win, the Queen congratulated the teenager, saying: “It is a remarkable achievement at such a young age, and is testament to your hard work and dedication.”
She added: “I have no doubt your outstanding performance, and that of your opponent Leylah Fernandez, will inspire the next generation of tennis players. I send my warmest good wishes to you and your many supporters.”
Boris Johnson wrote: “What a sensational match! Huge congratulations to @EmmaRaducanu.
“You showed extraordinary skill, poise and guts and we are all hugely proud of you.”
Labour leader Sir Keir Starmer tweeted: “What a winner. A true British hero. Congratulations @EmmaRaducanu on an inspirational win. From qualifier to champion without dropping a set. A phenomenal achievement.”
A tweet from the official account of the Duke and Duchess of Cambridge was signed C to signify Catherine, who is a huge tennis fan.
It said: “Huge congratulations @EmmaRaducanu on your stunning performances and historic Grand Slam victory! Incredible – we are all so proud of you.
“@leylahfernandez well done on your amazing achievements at this year’s #USOpen, it’s been a pleasure to watch. C”
Celebrity fans also added their voices to the long list of congratulations and praised both teenagers for their performances.
Pop group The Spice Girls, who first went on hiatus two years before Raducanu was born, tweeted “Wow! Amazing tennis from @leylahfernandez and @EmmaRaducanu that’s Girl Power right there!!
TV presenter Gary Lineker said: “First time in my life I’ve ever tweeted whilst on air but my goodness what a performance, what a triumph, what an amazing young woman,” he said.
“Congratulations @EmmaRaducanu on a truly staggering achievement. US Open winner at 18 without losing a set.
8 Out Of 10 Cats host Jimmy Carr described the teenager as a “legend” and admitted he had become emotional through the match.
“Emma Raducanu – 20 straight sets. What a performance? What a legend? The game I love played beautifully,” he tweeted.
“I think it’s OK I shed a tear. Congratulations Emma & also well done on those A Levels.”
Former Countdown host Carol Vorderman said: “Amazing…..huge congratulations to our new Queen of Tennis…. ”
Fellow athletes also took to social media to congratulate the champion.
Manchester United footballer Marcus Rashford tweeted: "Look at that bounce back @EmmaRaducanu US Open champion, amazing. Congratulations."
Manchester City footballer Jack Grealish wrote: "Absolutely unbelievable. An inspiration to everyone @EmmaRaducanu."
But people also praised the standard of play on both sides of the net.
Tennis legend Billie Jean King, who won a total of 39 Grand Slam titles, credited both women: "What a terrific display of competition & maturity from two exceptional players.
"It is wonderful to see this generation living our dream. "I can’t remember a #USOpen with better crowd support. Thank you, NY, the greatest fans in the world. "And congratulations, Emma!"
First Minister of Scotland Nicola Sturgeon added her congratulations.
“Just incredible! @EmmaRaducanu is a star, a role model and a champion. Congratulations!” she tweeted.
“I suspect tonight is one of these sporting occasions that will be talked about for decades to come.
“Two great players who will no doubt dominate women’s tennis for years to come.”
TV presenter Nick Knowles tweeted: “The quality of the us open tennis women’s final is epic!”