The American received a wild card into the tournament, 28 years after she first participated in it.
She had no idea she was the oldest player in the tournament so far.
I hadn't thought about it until it came out in the press. So yeah. Cheers! Here we go, she said at a press conference ahead of the tournament, according to AP.
She opens the tournament in Melbourne on Sunday against 24-year-old Olga Danilovic of Serbia, ranked 68th in the world. Williams is ranked 576th.
"In this situation, I need to be kind to myself. I'm playing well and doing what I need to do," Williams said.
Williams has previously won seven Grand Slam titles and four Olympic gold medals.
She made a comeback this summer after a 16-month hiatus and has only played sporadically on the tour in recent seasons.
