Top seed Novak Djokovic started his bid for a record seventh Australian Open title with a straight-set win over American qualifier Mitchell Krueger.
The 31-year-old Serb, chasing a 15th Grand Slam title and third in a row, won 6-3 6-2 6-2 on Rod Laver Arena.
Krueger broke Djokovic in the third game but the world number one dominated from there to seal victory in two hours and three minutes.
He will face French wildcard Jo-Wilfried Tsonga in the second round.
Djokovic's victory was in stark contrast to the way he lost a year ago to South Korea's Chung Hyeon in the last 16.
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He struggled with an elbow injury which would later require surgery and endured a string of poor results before hitting top form again to win Wimbledon and the US Open and regain the world number one ranking.
"It feels great to be healthy and back on this court again," said Djokovic, who was appearing in his 300th Grand Slam match.
"Twelve months ago it was quite a different sensation on the court with the elbow injury. Twelve months forward, obviously things are quite different."
Tsonga was on the losing side in the 2008 Australian Open final as Djokovic won his first of 14 Grand Slams.
Former world number four Tsonga missed seven months of 2018 after knee surgery and needed a wildcard to get into the tournament after his ranking dropped outside the top 200.
But the 33-year-old will be a dangerous opponent, having reached the semi-finals in his comeback tournament in Brisbane and beaten Martin Klizan of Slovakia in straight sets in the first round in Melbourne.
"It's funny, 11 years after our first Grand Slam final here - it feels like a lot has happened for both of us," Djokovic added.