Naomi Osaka overcame an attack of nerves and Serena Williams put on a "vintage" performance as the coronavirus-delayed Australian Open finally got underway on Monday.
World number two Simona Halep also breezed past Australia's Lizette Cabrera in straight sets in another convincing start by one of the tournament's leading lights.
Men's champion Novak Djokovic opens his bid for a record-extending ninth title in the evening session at Melbourne's Rod Laver Arena.
Form and fitness are highly unpredictable at the Australian Open after the coronavirus wiped out five months of last season and badly disrupted preparations for the first Grand Slam of 2021.
The Australian Open started three weeks late to allow players to quarantine and play warm-up events, which were suspended for a day last week after a coronavirus case at a tournament hotel.
After the tortuous build-up, third seed Osaka struck the first serve on the centre court against Russia's Anastasia Pavlyuchenkova and strode just 68 minutes later as a 6-1, 6-2 winner.
"I was really nervous coming into this match. I just wanted to play well," Osaka told a smattering of spectators on the socially-distanced court.
Williams started her quest for a record-equalling 24th Grand Slam title in style with a 6-1, 6-1 romp past Germany's Laura Siegemund in 56 minutes.
"This was a good start, it was vintage Serena," said the 39-year-old, playing an unparalleled 100th match at the tournament and turning heads in a brightly coloured, one-legged catsuit.
Later, the 2019 US Open champion Bianca Andreescu won an emotional first match after 15 months out against Romania's Mihaela Buzarnescu 6-2, 4-6, 6-3.
The 20-year-old Canadian last played at the WTA Finals in October 2019 at Shenzen, China, where she suffered the knee injury that scuppered her entire 2020 season.
French Open champion Iga Swiatek, 19, beat Arantxa Rus 6-1, 6-3 to reach the second round and continue her Grand Slam winning streak.
In the men's draw, third seed and US Open champion Dominic Thiem was made to work hard in the first set by Kazakh veteran Mikhail Kukushkin before coming through 7-6 (7/2), 6-2, 6-3.
"He's very experienced and the first set was super-challenging," said Thiem, beaten by Novak Djokovic in five epic sets in the Australian Open final last year.
Sixth seed Alexander Zverev dropped a set and smashed a racquet before grinding to a 6-7 (8/10), 7-6 (7/5), 6-3, 6-2 win against American Marcos Giron.
"He played incredible," said the German, who lost to Thiem in the final in New York and the Melbourne semi-finals last year.
"He had me on the ropes, particularly in the second set tie-break."
The tournament is known as the "Happy Slam" for its relaxed atmosphere but the pandemic has overshadowed the event this year with fewer spectators, mandatory mask-wearing and fans unable to circulate freely around the grounds.
Angelique Kerber, the 2016 Australian Open winner, was the first significant casualty of the women's championship when the 23rd-seeded German lost 6-0, 6-4 to 63rd-ranked American Bernarda Pera.
There were no such problems for the 2014 men's champion, Stan Wawrinka, as he reached the second round for a 16th straight time with a 6-3, 6-2, 6-4 win against Portugal's Paulo Sousa.
"It's always amazing and special to come back here. Winning my first Grand Slam was something unbelievable, amazing memories," said the 35-year-old Swiss 17th seed.
Milos Raonic, the 14th seed from Canada, also enjoyed serene progress through to the second round with a 6-3, 6-3, 6-2 win over Federico Coria of Argentina.
Bulgaria's Grigor Dimitrov got through in three sets against Croatia's Marin Cilic, the 2014 US Open champion.
But Gael Monfils, the French 10th seed, was stunned 3-6, 6-4, 7-5, 3-6, 6-3 by Emil Ruusuvuori of Finland, the world number 86, in three hours and 46 minutes.
Japan's Kei Nishikori also fell at the first hurdle with a straight-sets defeat to Pablo Carreno Busta of Spain.
Top women's seed Ashleigh Barty, defending champion Sofia Kenin and 20-time men's singles Grand Slam champion Rafael Nadal all begin their challenge on Tuesday.
Results from day one of the Australian Open at Melbourne Park on Monday:
Novak Djokovic (SRB x1) bt Jeremy Chardy (FRA) 6-3, 6-1, 6-2
Frances Tiafoe (USA) bt Stefano Travaglia (ITA) 7-6 (7/5), 6-2, 6-2
Reilly Opelka (USA) bt Lu Yen-hsun (TPE) 6-3, 7-6 (7/2), 6-3
Taylor Fritz (USA x27) bt Albert Ramos (ESP) 7-6 (8/6), 3-6, 6-2, 7-6 (8/6)
Stanislas Wawrinka (SUI x17) bt Pedro Sousa (POR) 6-3, 6-2, 6-4
Marton Fucsovics (HUN) bt Marc Polmans (AUS) 4-6, 6-3, 6-1, 6-7 (3/7), 6-3
Corentin Moutet (FRA) bt John Millman (AUS) 6-4, 6-7 (4/7), 3-6, 6-2, 6-3
Milos Raonic (CAN x14) bt Federico Coria (ARG) 6-3, 6-3, 6-2
Emil Ruusuvuori (FIN) bt Gael Monfils (FRA x10) 3-6, 6-4, 7-5, 3-6, 6-3
Pedro Martinez (ESP) bt Yoshihito Nishioka (JPN) 6-7 (3/7), 6-1, 6-1, 6-1
Alexander Bublik (KAZ) bt Aljaz Bedene (SLO) 6-4, 7-5, 5-7, 6-4
Dusan Lajovic (SRB x23) bt Sergiy Stakhovsky (UKR) 5-7, 6-4, 6-3, 5-7, 6-4
Adrian Mannarino (FRA x32) bt Dennis Novak (AUT) 6-2, 6-4, 7-6 (7/2)
Miomir Kecmanovic (SRB) bt Kamil Majchrzak (POL) 6-2, 6-4, 6-3
Maxime Cressy (USA) bt Taro Daniel (JPN) 7-6 (7/1), 7-6 (7/3), 6-4
Alexander Zverev (GER x6) bt Marcos Giron (USA) 6-7 (8/10), 7-6 (7/5), 6-3, 6-2
Dominic Thiem (AUT x3) bt Mikhail Kukushkin (KAZ) 7-6 (7/2), 6-2, 6-3
Dominik Koepfer (GER) bt Hugo Dellien (BOL) 7-5, 6-2, 6-4
Nick Kyrgios (AUS) bt Frederico Silva (POR) 6-4, 6-4, 6-4
Ugo Humbert (FRA x29) bt Yasutaka Uchiyama (JPN) 6-3, 6-4, 6-7 (3/7), 6-3
Grigor Dimitrov (BUL x18) bt Marin Cilic (CRO) 6-4, 6-2, 7-6 (7/5)
Alex Bolt (AUS) bt Norbert Gombos (SVK) 6-2, 6-2, 4-6, 6-3
Jiri Vesely (CZE) bt Kimmer Coppejans (BEL) 6-4, 3-6, 6-7 (3/7), 6-3, 6-3
Pablo Carreno-Busta (ESP x15) bt Kei Nishikori (JPN) 7-5, 7-6 (7/4), 6-2
Bernard Tomic (AUS) bt Yuichi Sugita (JPN) 3-6, 6-1, 4-1 ret
James Duckworth (AUS) bt Damir Džumhur (BIH) 6-3, 6-2, 6-4
Felix Auger-Aliassime (CAN x20) bt Cedrik-Marcel Stebe (GER) 6-2, 6-4, 6-2
Egor Gerasimov (BLR) bt Benoît Paire (FRA x25) 6-2, 2-6, 7-6 (7/5), 7-5
Aslan Karatsev (RUS) bt Gianluca Mager (ITA) 6-3, 6-3, 6-4
Alexandre Muller (FRA) bt Juan Ignacio Londero (ARG) 4-6, 6-3, 6-0, 6-3
Diego Schwartzman (ARG x8) bt Elias Ymer (SWE) 7-6 (7/3), 6-4, 2-6, 6-2
Bianca Andreescu (CAN x8) bt Mihaela Buzarnescu (ROM) 6-2, 4-6, 6-3
Hsieh Su-wei (TPE) bt Tsvetana Pironkova (BUL) 7-5, 6-2
Venus Williams (USA) bt Kirsten Flipkens (BEL) 7-5, 6-2
Sara Errani (ITA) bt Qiang Wang (CHN x30) 2-6, 6-4, 6-4
Marketa Vondrousova (CZE x19) bt Rebecca Peterson (SWE) 2-6, 7-5, 7-5
Rebecca Marino (CAN) bt Kimberly Birrell (AUS) 6-0, 7-6 (11/9)
Sorana Cirstea (ROM) bt Patricia Tig (ROM) 6-2, 6-1
Petra Kvitova (CZE x9) bt Greet Minnen (BEL) 6-3, 6-4
Zarina Diyas (KAZ) bt Tamara Zidansek (SLO) 6-2, 7-5
Bernarda Pera (USA) bt Angelique Kerber (GER x23) 6-0, 6-4
Ons Jabeur (TUN x27) bt Andrea Petkovic (GER) 6-3, 3-6, 6-4
Anna Karolina Schmiedlova (SVK) bt Mayo Hibi (JPN) 7-6 (7/2), 6-4
Caroline Garcia (FRA) bt Polona Hercog (SLO) 7-6 (8/6), 6-3
Naomi Osaka (JPN x3) bt Anastasia Pavlyuchenkova (RUS) 6-1, 6-2
Aryna Sabalenka (BLR x7) bt Viktoria Kuzmova (SVK) 6-0, 6-4
Darya Kasatkina (RUS) bt Katie Boulter (GBR) 6-1, 6-4
Alize Cornet (FRA) bt Valeria Savinykh (RUS) 6-2, 4-6, 7-6 (10/7)
Anastasia Potapova (RUS) bt Alison Riske (USA x24) 6-2, 6-1
Timea Babos (HUN) bt Ysaline Bonaventure (BEL) 7-6 (7/0), 6-4
Nina Stojanovic (SRB) bt Irina Begu (ROM) 6-3, 6-4
Serena Williams (USA x10) bt Laura Siegemund (GER) 6-1, 6-1
Iga Swiatek (POL x15) bt Arantxa Rus (NED) 6-1, 6-3
Camila Giorgi (ITA) bt Yaroslava Shvedova (KAZ) 6-3, 6-3
Fiona Ferro (FRA) bt Katerina Siniaková (CZE) 6-7 (5/7), 6-2, 6-4
Elena Rybakina (KAZ x17) bt Vera Zvonareva (RUS) 4-6, 6-4, 6-4
Veronika Kudermetova (RUS x32) bt Marta Kostyuk (UKR) 6-2, 7-6 (7/5)
Varvara Gracheva (RUS) bt Anna Blinkova (RUS) 6-1, 3-6, 7-6 (10/7)
Ajla Tomljanovic (AUS) bt Misaki Doi (JPN) 6-2, 6-1
Simona Halep (ROM x2) bt Lizette Cabrera (AUS) 6-2, 6-1