"Current WTA world number one Ashleigh Barty has today announced her retirement from professional tennis following a remarkable career at the top of the women's game," the WTA said in a statement this afternoon.
In a statement on Instagram, Barty said today was "difficult and filled with emotion for me" as I announce my retirement from tennis.
"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."
Barty will hold a press conference tomorrow.
"I don't have the physical drive, the emotional want and everything it takes to challenge yourself at the very top level anymore," she told close friend Casey Dellacqua in an Instagram video.
"I just know I am absolutely spent. I know physically I have nothing more to give and that for me is success. I've given absolutely everything I can to this beautiful sport of tennis and I'm really happy with that.
"I'm so happy, I'm so ready and I just know at the moment in my heart for me as a person that this is right," Barty added.
"I've done this before but [this is] a very different feeling. I'm so grateful for everything tennis has given me.
"It's given me all of my dreams and more, but I know that the time is right now for me to step away and chase other dreams, and put the racquet down."
Barty finishes her career with three major singles titles - the French Open (2019), Wimbledon (2021) and this year's Australian Open.
"I've had a lot of incredible moments in my career that have been pivotal moments, and Wimbledon last year changed a lot for me as a person and an athlete," she said.
"When you work so hard your whole life for one goal … to be able to win Wimbledon, which was the one true dream that I wanted in tennis, that really changed my perspective.
"I just had that gut feeling after Wimbledon and there was just a little part of me that wasn't quite satisfied, that wasn't quite fulfilled.
"And then came the challenge of the Australian Open and that just feels like my perfect way to celebrate what an amazing journey my tennis career has been."
Barty had previously stepped away from tennis in late 2014, before returning to the sport - following a stint playing cricket in the WBBL - in 2016.
She won her first major three years later and climbed to the top of the world rankings.
"There was a perspective shift in me in the second phase of my career that my happiness wasn't dependent on the results," Barty said.
"Success for me is knowing I've given absolutely everything I can. I know how much work it takes to bring the best out of yourself."
Barty said she wanted to explore other opportunities in her life outside of tennis.
"For me, Ash Barty the person has so many dreams that she wants to chase after that don't necessarily involve travelling the world, being away from my family, being away from home, which is where I want to be.
"I'll never, ever, ever stop loving tennis, it'll always be a massive part of my life. But now I think it's important that I get to enjoy the next phase of my life as Ash Barty the person, not Ash Barty the athlete.
"It was hard [making the decision to retire] but it's right and I know that brought me lots of comfort, knowing this is right for me. I am very excited."