<Table> <Tr> <Td> ← 2017 </Td> <Td> Australian Open </Td> <Td> 2019 → </Td> </Tr> </Table> <Tr> <Td> ← 2017 </Td> <Td> Australian Open </Td> <Td> 2019 → </Td> </Tr> <P> Roger Federer was the defending champion and successfully defended his title, defeating Marin Čilić in the final, 6--2, 6--7, 6--3, 3--6, 6--1 . It was Federer's 20th Grand Slam singles title and record - equalling sixth Australian Open men's singles title (tied with Roy Emerson and Novak Djokovic). With the win, Federer became the first male player to win at least six titles at two Grand Slam tournaments (six at the Australian Open and eight at Wimbledon). Federer became the oldest man to win a Grand Slam singles title in the Open era since Ken Rosewall in 1972 . The time span between Federer's first Grand slam glory at Wimbledon and this latest, almost 15 years, is an Open era record in the men's singles field . This was also the 10th time that Federer has defended a Grand Slam title, with the previous time being at the 2008 US Open . Čilić became the first Croatian player to reach a singles final at the Australian Open . </P> <P> Federer and Rafael Nadal were in contention for the ATP no . 1 singles ranking at the start of the tournament . Nadal ensured he would retain the top ranking by reaching the fourth round . It was the first time since 2011 Australian Open that Federer and Nadal were the first 2 seeds at a grand slam . </P>

Who wins the australian open men's single title in 2018