Former world No. 1 Caroline Wozniacki crashed out of the tennis season's opening grand slam after a shock defeat by Kazakhstan's Yulia Putintseva, ranked 58 places below the Dane.
Fans attempt to catch a stray tennis ball during the match between Wozniacki and Putintseva.
Defending champion Serena Williams got off to a better start than Wozniacki, beating Italy's Camila Giorgi 6-4 7-5. Ahead of the start of the Australian Open, the world No. 1 had been troubled by a knee injury.
Last year's losing finalist Maria Sharapova celebrates after an easy victory in her first-round match against Japan's grand slam debutante Nao Hibino.
Last week play had been suspended during qualifiers due to excessive heat. On Monday temperatures reached 35 Celsius (95 Fahrenheit),
World No. 1 and reigning Australian Open champion Novak Djokovic of Serbia cruised to a straight-sets victory over South Korea's Hyeon Chung.
Australian Nick Kyrgios blitzed Spain's Pablo Carreno Busta 6-2 7-5 6-2 to cruise into the second round.
Friend and fellow Australian tennis star Thanasi Kokkinakis, center, looks on as Kyrgios won his first-round match. The 19-year-old Kokkinakis, one of the youngest players in the world top 100, suffered a shoulder injury in December that ruled him out of the tournament.
Canada's Eugenie Bouchard had a difficult 2015 season after reaching the quarterfinals in Melbourne, but made a positive start to this year's event by defeating Serbia's Aleksandra Krunic 6-3 6-3.
Switzerland's third seed Roger Federer, seeking his fifth Australian Open title, acknowledges the crowd after winning his first-round match against Georgia's Nikoloz Basilashvili.
Melbourne Park's main stadium, the Rod Laver Arena, is pictured during the first-round match between Kristyna Pliskova and Australian 25th seed Samantha Stosur, which was won by the Czech player.