Defending champion Novak Djokovic began his Australian Open title defence with a landmark 900th career victory as the top seeds all won on an opening day where heavy rains suspended play on the outer courts.
Djokovic beat Germany's Jan-Lennard Struff 7-6(5) 6-2 2-6 6-1 to advance to the second round as the Serb looks to win a record-extending eighth title at Melbourne Park.
"I'm just starting," he joked when he was told it was his 900th win on the Tour. "I thought I started off well. He came back, he turned it around, he was not missing much. Credit to him for fighting, he's a very powerful player," Djokovic said.
Third seed Roger Federer also sailed into the second round with a straight sets 6-3 6-2 6-2 victory over American Steve Johnson but Canadian 13th seed Denis Shapovalov was shocked 6-3 6-7(7) 6-1 7-6(3) by Hungarian Marton Fucsovics.
"I just haven't played proper matches in many, many weeks, and a lot of guys, probably 95% of the guys, are coming here with matches," Federer told reporters.
"For me really the first three rounds are key to get going, to get used to the pressure, stay calm, when to save breakpoint or 30-all points or whatever it may be, or just to stay calm if you're down a set and a break or whatever it might be.
"This is sort of the unknown that can be a little bit scary at times. But today there was none of that because I broke early each set and was able to get on a roll, play freely after that ... I felt like I had the game under control."
Serena Williams, looking to win a record-equalling 24th Grand Slam title, advanced after trouncing Anastasia Potapova 6-0 6-3 while defending champion Naomi Osaka was untroubled by Marie Bouzkova in her 6-2 6-4 victory.
World number one Ash Barty dropped a set but fought back to beat Lesia Tsurenko 5-7 6-1 6-1, keeping alive Australia's hopes of having a first women's champion since 1978.
American teenager Coco Gauff was drawn against her idol Venus Williams once again at a Grand Slam and the 15-year-old prevailed on her main draw debut with a 7-6(5) 6-3 victory.
Gauff, who stunned fellow American Venus Williams in the first round of Wimbledon last year, produced another superb performance to beat the 39-year-old seven-times Grand Slam winner 7-6(5) 6-3.
"I was really nervous for today's match. I was shocked when I saw the draw," Gauff said in a courtside interview before addressing the Margaret Court Arena crowd.
"I just want to say thank you guys so much. You guys were chanting my name and I only thought that would happen at the U.S. Open."
World number one and top seed Rafa Nadal begins his quest to equal Federer's record of 20 Grand Slam titles when he takes on Bolivian Hugo Dellien on Wednesday.