"Today is a difficult and emotional day for me because I am announcing my retirement from tennis," the Australian said on Instagram.
"I'm so happy, and I'm so ready and I just know now in my heart that as a person, it's the right decision," she said, in tears, alongside her former doubles partner Casey. Dellacqua.
World number one since 2019, she has won three Grand Slam singles titles, at Roland-Garros in 2019, then at Wimbledon in 2021 and at the Australian Open this year.
In January, she became the first local champion in 44 years to win the Australian Open, joining the exclusive club of Grand Slam crowns on three different surfaces.
“I am so grateful for everything tennis has given me, it has given me all my dreams and more,” added the champion.
"But I know the time has come for me to step away, pursue other dreams and put the rackets down."
"Thank you for being an incredible ambassador for this sport and for women around the world," the Women's Tennis Association (WTA) tweeted.
"We will miss you very much, Ash".
Barty, one of the most respected and loved players on the tour, quickly became the best, with her dizzying range of slices, precise serves and flawless forehand.
She got engaged last year to longtime boyfriend Garry Kissick, who was always on the court when she played.
© 2022 AFP