Two-time defending champion Novak Djokovic[1] defeated Daniil Medvedev in the final, 7–5, 6–2, 6–2 to win the men's singles tennis title at the 2021 Australian Open.

1 and four-time major champion Carlos Alcaraz; he lost to Mikael Ymer in the second round.

At 17 years old, Alcaraz became the youngest man to win a main-draw match at the Australian Open since Bernard Tomic in 2009.

Aslan Karatsev became the first male qualifier to reach a major semifinal since Vladimir Voltchkov in the 2000 Wimbledon Championships, and the first since Bob Giltinan in December 1977 to do so at the Australian Open.

[7] This was the first major in the Open Era to feature three Russian men in the quarterfinals, those being Karatsev, Medvedev and Andrey Rublev.