- Venue: Melbourne Park
- Date: 16-29 January
- Time: 0000 GMT
Coverage: Watch live on Eurosport; singles finals and one men's semi-final on BBC Two/Red Button/HD channel/website; listen on BBC Radio 5 live; text commentaries and reports on the BBC Sport website
Serena Williams has never lost in the first round in her 46 grand slams
Serena Williams overcame a late start and a tenacious opponent to reach the second round of the Australian Open.
The former champion and 12th seed hit 34 winners but also made 26 unforced errors in beating Austria's Tamira Paszek 6-3 6-2.
The match started at 2330 local time following Lleyton Hewitt's four-hour win over German Cedrik-Marcel Stebeand.
Elsewhere, US Open champion and sixth seed
lost 7-6 (7-2) 6-3 to world number 59 Sorana Cirstea.
After her early-hours victory Williams, who missed the tournament through injury in 2011, having won the title in 2009 and 2010, told the Rod Laver Arena crowd: "I haven't been here for a year but thank you for getting me though it.
“I really, really wanted to do well here and I did everything I could to try to give myself a good opportunity. But it obviously didn't happen.”
"I'm definitely a night owl and can stay up all night. I really don't like mornings, but I don't mind them during a tournament."
The 13-time Grand Slam winner and five times Australian Open champion has now won 15 consecutive matches at Melbourne Park.
Williams's participation in this year's event had appeared in doubt after she injured her ankle in Brisbane two weeks ago but she moved well throughout the match and did not appear hampered by the injury.
The late hour seemed to affect the 30-year-old, who struggled to subdue the challenge from the unheralded Paszek.
She appeared frustrated at times as she alternated between making scintillating winners and simple errors.
But although Paszek fought hard throughout, the power of Williams proved decisive and the American next plays Czech Barbora Zahlavova Strycova.
shock exit saw the 27-year-old home favourite beaten in straight sets 7-6 (7-2) 6-3 by Romanian Cirstea.
Her defeat continued a woeful run of form in Australia, taking her tally to one win in three tournaments this year.
The Australian saved three match points on her own serve but a looping forehand that drifted long ended her participation, and prolonged the search for a first home winner since 1978.
"I am extremely disappointed," said the Australian.
"It's certainly not what I wanted, not just this tournament but the whole [Australian] summer.
"I think it was one of those matches where I wasn't taking charge and she was playing super aggressive.
"I really, really wanted to do well here and I did everything I could to try to give myself a good opportunity. But it obviously didn't happen."
Stosur's first-round loss is an echo of
departure from the 2011 US Open, the Czech exiting in the first round in New York after winning Wimbledon.
But there was no danger of the powerful second seed stumbling at the first hurdle in Melbourne as she swept past Dushevina 6-2 6-0.
Kvitova's win means Caroline Wozniacki must reach at least the quarter-finals to have a chance of retaining the world number one ranking, while Agnieszka Radwanska - one of four other players who had been in with a chance of becoming world number one at this tournament - is no longer in contention.
also safely negotiated her path to round two, dropping just one game in her victory over Argentine Dulko.
Elsewhere, seventh seed
won in three sets against Alexandra Dulgheru and ninth seed
beat Virginie Razzano 7-5 6-0.
Number 14 seed
survived a scare to beat Stefanie Voegele 6-2 4-6 6-4.
, seeded 18th, also dropped a set on her way to victory over Chanelle Scheepers.
Number 15 seed
, 17th seed
, 27th seed
, Serbian and 21st seed
, 30th seed
and home favourite