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.
Williams lost the Australian Open final last year to Angelique Kerber but won Wimbledon to equal Steffi Graf’s Open era record of 22 Grand Slam singles titles.
She has barely played since the US Open last September because of injury, and lost in the second round of this month’s Auckland Classic.
But she eased doubts about her form and fitness with a typically powerful performance in temperatures of about 35C.
Williams will face Lucie Safarova in the second round after the 29-year-old Czech saved nine match points before beating Belgium’s Yanina Wickmayer 3-6 7-6 (9-7) 6-1