In an Instagram post shared almost immediately after Raducanu's U.S. Open win, the official Duke and Duchess of Cambridge account uploaded a celebratory image of the British tennis star with a caption that read, "Huge congratulations @EmmaRaducanu on your stunning performances and historic Grand Slam victory! Incredible — we are all so proud of you."

Speaking in the same post, Middleton also paid tribute to Raducanu's Canadian rival Fernandez. "@LeylaHannietennis well done on your amazing achievements at this year's #USOpen, it's been a pleasure to watch. C," the Duchess wrote. 

Middleton wasn't the only senior member of the royal family to celebrate Raducanu's U.S. Open victory, and Her Majesty the Queen also left a message of congratulations following her win.

"I send my congratulations to you on your success in winning the United States Open Tennis Championships. It is a remarkable achievement at such a young age, and is testament to your hard work and dedication." The statement released by Queen Elizabeth II continued, "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."