TENNIS superstar Serena Williams has taken to Snapchat to announce she is pregnant.

The 23-time grand slam singles champion posted a picture overnight, showing off a prominent baby bump with the caption “20 weeks”.

That means Williams was pregnant when she won the Australian Open in January.

Williams’ spokeswoman has told Reuters she will not play again this year, but will return to the WTA circuit in 2018.

The 35-year-old announced her engagement to tech entrepreneur Alexis Ohanian, best known as the co-founder of Reddit, in December.

Williams’ pregnancy is exciting enough, but the news that she was pregnant during the year’s first grand slam has left fans in awe.

By the way, she didn’t even drop a set at the Australian Open.

Serena Williams was pregnant when she won her 23rd grand slam tournament at the Australian Open. And did not drop ONE SET. Let that sink in. — 23RENA (@noelleharmony) April 19, 2017

Serena Williams was pregnant when she won the Australia Open in Jan. but I cant even get out of bed when I'm on my period. Sis is superwoman — Taryn Finley (@_TARYNitUP) April 19, 2017

Congrats to Serena Williams' unborn child and future Grand Slam record holder — Charlotte Wilder (@TheWilderThings) April 19, 2017

Can't wait for 53-year old Serena and her kid to win the 2034 Wimbledon doubles title (mixed doubles if its a boy) — Rodger Sherman (@rodger_sherman) April 19, 2017

Among active tennis players, Williams holds the most major titles in singles, doubles, and mixed doubles combined. More importantly, she’s hot on the heels of Margaret Court’s all-time grand slam singles titles record of 24.

SERENA’S CLASSY TRIUMPH

Williams won her 23rd title by beating her sister, Venus, 6-4 6-4 in the final. It was the seventh time she had won the decider at Melbourne Park.

After trying to outdo each other on court, Serena and Venus were at it again on the dais during the post-match presentation. It was as if each sister wanted to be the most polite, the most gracious and the most humble - there was some seriously classy sportsmanship on show.

“Serena Williams — that is my little sister guys,” Venus said. “Your win has always been my win. I think you know that.

“All the times I wasn’t there or couldn’t be there or didn’t get there, you’ve been there.

“I’m enormously proud of you, you mean the world to me.”

Asked in her press conference if it was difficult to be happy for her sister because she was disappointed she didn’t win, Venus’ response was exactly what you’d expect.

“No, because I guess I’ve been here before, you know. I really enjoy seeing the name Williams name on the trophy. This is a beautiful thing.”

Serena too showered her older sister with love in front of an adoring crowd.

“I would really like to take this moment to congratulate Venus, she is an amazing person,” Serena said. “There is no way I would be at 23 (grand slam titles) without her. There is no way I would be at one without her.

“She is my inspiration, she is the only reason I am standing here today and the only reason that the Williams sisters exist. Thank you Venus for inspiring me to be the best player that I could be and inspire me to work hard.

“Every time you won this week I felt like I got a win too.

“Thank you so much. Thank you.”

‘GREATEST SPORTS STORY EVER’

Even before the match, former Aussie pro Rennae Stubbs called the Williams sisters’ journey “the most incredible story in sports”.

The four-time grand slam doubles champion first met the pair before they were even teenagers, and has been a fan ever since. Her appreciation of both women, and Serena in particular, only grew after the younger sibling racked up major title number 23.

“Greatest siblings ever in tennis. Greatest sports story ever,” Stubbs told Serena in the Channel Seven studio.

“Serena is just more aggressive. That is who she is and how she has come through her entire career and that is what makes her a little bit better.

“Every single time we think that there is vulnerability, she comes back and dominates this tournament without losing a set. This is the most dominant player that we have ever seen.

“She will go down as the greatest athlete we’ve ever seen. Not man, not woman. Athlete.”

With today’s news, Williams’ already astonishing achievement at Melbourne Park just got even more impressive.