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The reigning Australian Open and Wimbledon champion, who hasn't played since breaking the 44-year local title drought at Melbourne Park in January, posted the news on social media on Wednesday.
"Today is difficult and filled with emotion for me as I announce my retirement from tennis," Barty posted on Instagram.
"I am so thankful for everything this sport has given me and leave feeling proud and fulfilled.
"Thank you to everyone who has supported me along the way, I'll always be grateful for the lifelong memories that we created together."
It's the second time Barty has walked away from tennis, the three-time grand slam champion taking a 16-month sabbatical after a first-round loss at the 2014 US Open.
But, unlike then when she was a homesick teenager, this time Barty says she's quitting for good.
"I will be retiring from tennis. It's the first time I've said it out loud and it's hard to say but I'm so happy and so ready," she said.
"I just know at the moment in my heart for me as a person this is right.
"I've done this before but it's a very different feeling.
"I'm so grateful for everything tennis has given me.
"It's given me all of my dreams plus more but I know that the time is right now for me to step away and chase other dreams and to put the racquets down."
Last time she stopped playing, Barty played professional cricket for the Brisbane Heat in the WBBL.
The sporting super talent could conceivably pursue a professional golf career next.
A four-marker, Barty won the A grade club championship two years ago at Brisbane's Brookwater Golf Club, where she met her now-fiance and PGA trainee pro Gary Kissick.
Both Barty's parents were state amateur golf representatives.
Whatever she pursues, Barty's tennis legacy is secure.
Two weeks after winning the French Open in 2019, Barty became the first Australian woman to reach world No.1 since her mentor and Indigenous idol Evonne Goolagong 43 years earlier.
She followed that up with victory at the 2019 WTA Finals in Shenzhen, in doing so pocketing $US6.4 million - the biggest cheque in tennis history.
Her crowning glory came last year at Wimbledon before Barty defied intense pressure and expectations from home fans to win the Australian Open.
"(Retirement) is something I've been thinking about for along time and I've had a lot of incredible moments in my career that have been pivotal moments," Barty said in a video interview with her great mate and former doubles partner Casey Dellacqua.
"Wimbledon last year changed a lot for me as a person and for me as an athlete.
"You work so hard your whole life for one goal and I've been able to share that with so many incredible people but to be able to win Wimbledon was my dream.
"The one true dream that I really wanted in tennis. That really changed my perspective and I just had that gut feeling after Wimbledon and had spoken to my team about it."
But after a semi-final and two quarter-final defeats at Melbourne Park, Barty had one more piece of unfinished business to tend to.
"There was a little part of me that wasn't quite satisfied, wasn't quite fulfilled and then came the challenge of the Australian Open and that for me feels like the most perfect way, my perfect way to celebrate what an amazing journey my tennis career has been."
That was the Queenslander's 15th career title - and seemingly last.
She would have been chasing a career grand slam at this year's US Open in September.
Instead Barty leaves the sport having held the top ranking for 114 weeks, the eighth-longest tenure in history behind only all-time greats Steffi Graf, Martina Navratilova, Serena Williams, Chris Evert, Martina Hingis, Monica Selesand Justine Henin.