Serena Williams has survived an early scare to win her first round match at the Australian Open.

Williams defeated Italian Camila Giorgi 6-4, 7-5.

The six-time Australian Open champion needed one hour and 45 minutes to complete the win in sweltering conditions at Melbourne Park.

It was Williams' first match since her US Open semifinal loss, with the 34-year-old recovering from a knee injury.

She will play either Latvia's Jelena Ostapenko or Taiwan's Su-Wei Hsieh in the second round.

Meanwhile, Chinese qualifier Qiang Wang caused the first major upset of the tournament, knocking out 24th seed and 2013 semi-finalist Sloane Stephens 6-3, 6-3.