The 23-time singles Grand Slam champion's 7-5 6-7(4) 6-1 defeat sparked a flood of messages on social media, as current and former athletes across sport, as well as the world at large, celebrated her achievements of the last 25 years.

MICHELLE OBAMA

"Congrats on an amazing career, @SerenaWilliams! How lucky were we to be able to watch a young girl from Compton grow up to become one of the greatest athletes of all time.

"I'm proud of you, my friend - and I can't wait to see the lives you continue to transform with your talents."

FORMER NO.1 BILLIE JEAN KING

"Her incredible career made its mark on tennis history. And yet her greatest contributions may be yet to come. Thank you, @serenawilliams. Your journey continues."

SWIMMING LEGEND MICHAEL PHELPS

"Her tennis accomplishments speak for themselves, but one of the things I admire about her is she simply doesn't quit.

"On or off the court her will, her strength, her determination... she simply never gives up. She’s a great example to us all."

GOLF GREAT TIGER WOODS

"@serenawilliams you're literally the greatest on and off the court. Thank you for inspiring all of us to pursue our dreams. I love you little sis," he tweeted.

COCO GAUFF

"The impact you've had on me goes beyond any words that can be put together and for that I say thank you, thank you, thank you, GOAT."

AUSTRALIAN PLAYER AJLA TOMLJANOVIC

"I'm feeling really sorry just because I love Serena just as much as you guys do. What she's done for me, for the sport of tennis, is incredible.

"I never thought I'd have a chance to play her in her last match when I remember watching her in all those finals, so this is a surreal moment for me.

"I just thought she would beat me, so the pressure wasn't on me. Even to the last point, I knew she's in a position to win even when she's down 5-1. That's just who she is and she's the greatest of all time. Period."

FORMER WORLD NUMBER ONE ANDY RODDICK

"I love you @serenawilliams It's been the pleasure of a lifetime to watch you become what you have. Can't wait to see what you do next. Thank you my old friend."

AMERICAN SOCCER PLAYER ALEX MORGAN

"Serena fighting until the last point, always. You've given so much to tennis, and so much to women's sports. Thank you @serenawilliams."

AUSTRALIAN PLAYER DARIA SAVILLE

"I feel so emotional realising that this was Serena's last match. I have a feeling she might reconsider? I don't know."

FORMER WORLD NUMBER FOUR JAMES BLAKE

"Serena. Thank you for being you and the inspiration to so many men and women. I've never seen a more intense competitor and it was an honour to share a court with you and watch history. Simply the best. @serenawilliams."