Ash Barty has announced a shock retirement from tennis at just 25.

The Australian world number one announced the decision via her Instagram feed.

"I am so thankful for everything this sport has given me and leave feeling proud and fulfilled," she said.

"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 has not played since winning the Australian Open final over Danielle Collins in January.