Novak Djokovic chases a second consecutive and an eighth overall title in Melbourne, while Dominic Thiem looks for a first Grand Slam title
Sofia Kenin could become the first American in three years to win the Australian Open, while Garbine Muguruza searches for a third Grand Slam title.
Kenin has overcome an extraordinary journey from Moscow to Miami, and now needs one more win in Melbourne to capture her first major tennis title.
The winners of the last five Australian Opens meet in the semifinals at Melbourne Park for the first time since 2016.
The world No. 1 takes on No. 5 seed Dominic Thiem, while 2014 Australian Open champion Stan Wawrinka plays No. 7 Alexander Zverev.
"I found it a bit tough," He added. "It's not like I'm known to throw around words and whatever. It's not like the whole stadium heard it either, but no problem, I'll accept it," Federer said of the violation.
Federer takes on Tennys Sandgren of the U.S., while Djokovic faces No. 32 seed Milos Raonic of Canada.
The world No. 1 takes on Spain's Pablo Carreno Busta, while Medvedev plays Australia's Alexei Popyrin.
The 23-Grand Slam winner suffered a shock third round loss against 6-4, 6-7 (2-7), 7-5 to China's Wang Qiang.
The 15-year-old American and the two-time Grand Slam winner cross paths in a major tournament for the first time since the U.S. Open last year.
Williams faces China's Wang Qiang, while Federer takes on Australia's John Millman and Coco Gauff plays Naomi Osaka.
The world No. 1 takes on Argentina's Federico Delbonis, while Medvedev plays Spanish qualifier Pedro Martinez.
The 15-year-old sensation could meet defending champion Naomi Osaka in the third round if she defeats the Romanian in the second round.
Williams faces Slovenia's Tamara Zidansek, while Federer takes on Serbia's Filip Krajinovic and Djokovic plays Japan's wild card Tatsuma Ito.
The world No. 1 makes his tournament debut against world No. 72 Hugo Dellien of Bolivia, while world No. 2 Karolina Pliskova headlines the women's tournament.
The two Americans meet in the first round of the Australian Open six months on after Gauff knocked Williams out of Wimbledon.
The first Grand Slam of the season begins in Melbourne on Monday, with some of the tournament favorites all in action.
The 108th edition of the Australian Open gets underway in Melbourne on Monday, with the women's and men's final scheduled for the first weekend of February.
Novak Djokovic and Serena Williams are the bookmakers' favorite to add an eighth Australian Open title to their collections this year.
The first Grand Slam tournament of 2020 gets underway on January 20 in Melbourne with Novak Djokovic and Naomi Osaka looking to defend their titles.
Roger Federer, Novak Djokovic, Rafael Nadal and Serena Williams are among the players in action in the fundraiser for the victims of the bushfires.
Environmental activists have called for Federer to cut ties with a company that has invested millions in fossil fuel.
Nissin's ads depicted the Japanese tennis champ with a much whiter skin tone and a narrower nose.
The tennis star thinks Maria Sharapova "might be perceived by the public as nicer."
The Briton has suffered with injury this year.
Sharapova beat Roberta Vinci upon her return from her doping ban on Wednesday.
Williams won her 23rd Grand Slam singles title at the Australian Open in January, when she was already close to two months pregnant.