The 2018 Australian Open was a tennis tournament played at Melbourne Park between 15 and 28 January 2018, and was the first Grand Slam tournament of the 2018 season. The tournament consisted of events for professional players in singles, doubles and mixed doubles play. Junior and wheelchair players compete in singles and doubles tournaments. Roger Federer was the defending champion in the men's singles event and successfully retained his title, his record twentieth Grand Slam major overall, defeating Marin Čilić in the final, while Caroline Wozniacki won the women's title, defeating Simona Halep in the final to win her first Grand Slam.

Marin Čilić is a Croatian professional tennis player. Čilić has won 20 ATP Tour singles titles, including a major at the 2014 US Open. He was also runner-up at the 2017 Wimbledon Championships and the 2018 Australian Open, and won a silver medal at the 2020 Tokyo Olympics in the men's doubles tournament partnering Ivan Dodig. His career-high singles ranking is world No. 3, achieved on 28 January 2018. Čilić has reached the semifinal stage or better at all four majors, and the quarterfinal stage or better at all nine ATP Masters 1000 tournaments. He is one of six active players with at least 20 ATP Tour titles and one of the five active players to reach at least the semifinal stage at all four majors. Alongside compatriot Goran Ivanišević, Čilić is widely considered to be one of the greatest Croatian tennis players in history.