SYDNEY -- Australian tennis women's world No 1 Ashleigh Barty has announced her retirement from the sport, saying she has lost the drive to compete at the highest level.

"I don't have the physical drive, the emotional want and everything it takes to challenge yourself at the very top level anymore," she said in a video posted on social media on Wednesday.

"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," the 25-year-old said.

In an emotional interview with a close friend, Barty said she was "absolutely spent" when it came to tennis.

"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," said Barty.

"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."

The announcement came two months after Barty became the first Australian to win the Australian Open since 1978.

The Australian tennis star finishes her career with three Grand Slam titles - the French Open in 2019, Wimbledon in 2021 and this year's Australian Open, where she beat out American Danielle Collins in the final.

"As a person, this is what I want. I want to chase after some other dreams that I've always wanted to do, and always had that really healthy balance, but I'm really, really excited," said Barty.

Following her Australian Open triumph, Barty withdrew from Indian Wells and the Miami Open, saying her body needed more time to recover.

Wednesday's announcement marked the second time Barty has walked away from tennis, previously taking a hiatus to play cricket in 2014 before returning in 2016.