2018 Australian Open – Men's singles
Defending champion Roger Federer defeated Marin Čilić in the final, 6–2, 6–7, 6–3, 3–6, 6–1 to win the men's singles tennis title at the 2018 Australian Open. It was his record-equalling sixth Australian Open title (tied with Roy Emerson and Novak Djokovic) and record-extending 20th major title overall. With the win, Federer became the oldest man to win a major singles title since Ken Rosewall in 1972. This was the 10th time that Federer defended a major title, with the previous time being at the 2008 US Open. Čilić became the  first Croatian to reach an Australian Open singles final. Federer and Rafael Nadal were in contention for the world No. 1 singles ranking. Nadal retained the top ranking by reaching the fourth round. It was the first time since the 2011 Australian Open that Federer and Nadal were the top two seeds at a major. Nadal attempted to become the first man in the Open Era and the third man ever to achieve a double career Grand Slam, but retired in the quarterfinals due to injury. This was the first time since the 2008 Wimbledon Championships that two unseeded players  (Chung Hyeon and Kyle Edmund) reached the semifinals of a major men's singles event, and the first time at the Australian Open since 1999. Chung became the first South Korean player to reach the quarterfinals and semifinals of a major event. Novak Djokovic's fourth-round loss to Chung was his first straight-sets loss at the Australian Open since 2007. This marked the last Australian Open appearance for 2006 finalist and former world No. 8 Marcos Baghdatis. Seeds. All seedings per ATP rankings.