2021 Australian Open – Men's singles

Two-time defending champion Novak Djokovic 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. It was his record-extending ninth Australian Open title and 18th major title overall. With his fourth-round win, Djokovic joined Roger Federer as only the second man to achieve 300 match wins in majors.

Aslan Karatsev was the first male qualifier to reach a major semifinal since Vladimir Voltchkov in the 2000 Wimbledon Championships, and the first at the Australian Open since Bob Giltinan in December 1977. Ranked world No. 114, he was the lowest-ranked player to reach a major semifinal since Goran Ivanišević (ranked No. 125) at the 2001 Wimbledon Championships, the lowest ranked to do so at the Australian Open since Patrick McEnroe (also ranked No. 114) in 1991, and the first man in the Open Era to reach the semifinals on his major main-draw debut.

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

This marked the first major main-draw appearance of future world No. 1 and five-time major champion Carlos Alcaraz; he lost to Mikael Ymer in the second round. At 17 years old, Alcaraz was the youngest man to win a main-draw match at the Australian Open since Bernard Tomic in 2009.