Ash Barty, the world No. 1 women's tennis player, has surprised the sporting world by retiring at the age of 25, only two months after winning her third Grand Slam singles title at the Australian Open.

"Tennis has given me all of my dreams plus more but I know that the time is right now for me to step away," Barty said in a sometimes emotional but largely calm six-minute video on posted on her Instagram account.

"I don't have the physical drive, the emotional want and everything it takes to challenge yourself at the very top level any more. I am spent," she explained in a short interview with her friend and former doubles partner Casey Dellacqua.

Barty won the 2019 French Open, as well as Wimbledon and the Australian Open in Melbourne Park last year. She became the first Australian player in 44 years to win at her home event in January, beating four U.S. tennis stars on the way.

Barty previously left the tour for nearly two years in 2014, citing burnout, but came back to rise to the top of the sport.

"I know that people may not understand it, I'm OK with that," she said. "I have given everything I can to this beautiful of sport and I'm really happy with that. For me that is my success."

Barty explained that she wanted to "chase other dreams" that "don't necessarily involve traveling the world being away from my family." Barty announced her engagement to trainee golf professional Garry Kissick in November.

Tributes came in online. British men's grand slam winner Andy Murray wrote: "Happy for Ash Barty, gutted for tennis, what a player." Barty plans a media conference on Thursday.

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