Six-time Australian Open champion, Serena Williams progressed to the second round with a straight-set win over Swiss teenager Belinda Bencic.
The American, 35, beat her 19-year-old opponent 6-4 6-3 in 79 minutes in scorching conditions in Melbourne.
The world number two, attempting to win a record 23rd Grand Slam singles title, said she “has nothing to lose”.
“Every match I’m playing for fun. I get to travel the world and do what I do best – play tennis,” she added.
Defending champion Novak Djokovic reached the second round of the Australian Open by beating Spain’s Fernando Verdasco in straight sets.
The 12-time Grand Slam champion secured a 6-1 7-6 (7-4) 6-2 victory in an entertaining match in Melbourne. World number nine Rafael Nadal earlier reached the second round with a commanding display.
The injury-hit Spaniard, who lost in the first round last year, beat Germany’s Florian Mayer 6-3 6-4 6-4.
“It feels like home,” said Djokovic. “It feels like coming to the place where I have an amazing number of incredible memories.
Nadal, 30, had played just four matches since September’s US Open after struggling last year with a wrist injury.
He dominated Mayer from the start, taking just over two hours to secure a straight-set victory in 39 degree heat.
“I was healthy enough to practise the way I wanted to, so that’s important for me,” Nadal added.
“I’ve had a longer period of time here in Australia, it was great experience and I was able to play in Brisbane.”