Serena Williams will not defend her title at Melbourne Park this month after withdrawing from the Australian Open.

The 23-time grand slam champion joins the growing list of absentees for the year's opening major, which already includes five-time runner-up Andy Murray and former world number four Kei Nishikori, with doubts also over star duo Novak Djokovic and Rafael Nadal.

Serena has not played a competitive match since claiming a record-equalling slam at the Australian Open last year, having given birth to her first child in September.

The 36-year-old American featured in an exhibition match in Abu Dhabi and lost to Jelena Ostapenko, and she was non-committal on her Australian Open plans following the outing, while she turned down the offer for a wildcard to the Sydney International.

"After competing in Abu Dhabi I realised that although I am super close, I'm not where I personally want to be," Williams said.

"My coach and team always said 'only go to tournaments when you are prepared to go all the way'. I can compete – but I don't want to just compete, I want to do far better than that and to do so, I will need a little more time.

"With that being said, and even though I am disappointed about it, I've decided not to compete in the Australian Open this year.

"The memory of last year's Open is one that I will carry with me, and Olympia and I look forward to coming back again.

"I appreciate the support and understanding of my fans and everyone at the Australian Open."