Defending Australian Open champion Novak Djokovic won his longest first-round Grand Slam match after being tested by qualifier Dino Prizmic.

The Serb, chasing a record-extending 11th men's title, needed four hours and one minute to beat the 18-year-old Croat 6-2 6-7 (5-7) 6-3 6-4.

Prizmic, playing in his first Grand Slam match, saved six match points before Djokovic secured victory.

"He gave me a run for my money," Djokovic said in an on-court interview.

The 36-year-old, who is aiming for a record 25th Grand Slam singles title, will face Alexei Popyrin or Marc Polmans in the second round.

In rallies which echoed those in matches between Djokovic and world number two Carlos Alcaraz, world number 178 Prizmic sprinted and stretched all over the court to excite the Melbourne night-session crowd.

The match surpassed Djokovic's previous longest in the first round of a major, which was a three-hour-57-minute encounter against Gael Monfils at the US Open in 2005.

"He deserves all the applause. He is an amazing player, he handled himself incredibly well on the court. This is his moment," Djokovic said.

"It could easily have been his match as well. He showed great mentality and resilience.

"I certainly want to be in his corner. So hopefully he will invite me because he will make some big things in his career that's for sure."

Fifth seed Andrey Rublev survived a comeback from world number 78 Thiago Seyboth Wild to win a five-set thriller 7-5 6-4 3-6 4-6 7-6 (10-6), while Croatia's 2018 runner-up Marin Cilic lost 6-1 2-6 6-2 7-5 to Hungarian Fabian Marozsan.

Former semi-finalist Matteo Berrettini withdrew before his first-round match against Stefanos Tsitsipas because of a foot injury, meaning the Greek seventh seed will instead play Belgian Zizou Bergs.

The Australian Open has been extended to 15 days this year in an attempt by organisers to avoid late finishes - with this its first Sunday start.