2021 US Open – Men's singles

Daniil Medvedev defeated Novak Djokovic in the final, 6–4, 6–4, 6–4 to win the men's singles tennis title at the 2021 US Open. It was his first major title. Medvedev became the third Russian man, after Yevgeny Kafelnikov and Marat Safin, to win a major singles title, and the first to do so since Safin at the 2005 Australian Open. He lost just one set during the tournament, against Botic van de Zandschulp in the quarterfinals. Djokovic was aiming to become the second man in the Open Era, after Rod Laver in 1969, to complete the Grand Slam. He was also attempting to win an outright record 21st major singles title and surpass his Big Three counterparts, Roger Federer and Rafael Nadal. By reaching the final, Djokovic tied Federer's record of 31 men's singles major finals contested, and repeated his 2015 achievement of contesting the maximum-possible 28 major singles matches in a season. This marked Djokovic's record sixth runner-up finish at the event.

Dominic Thiem was the reigning champion, but did not participate due to an ongoing wrist injury.

By defeating world No. 3 Stefanos Tsitsipas in the third round, Carlos Alcaraz became the youngest man to beat a top 3 ranked-player in singles at the US Open since the inception of the ATP rankings in 1973. He became the youngest male quarterfinalist at a singles major since Michael Chang at the 1989 French Open, and the youngest at the US Open in the Open Era; he would go on to win the title the following year. Van de Zandschulp became the first Dutchman to reach a singles major quarterfinal since Sjeng Schalken at the 2004 Wimbledon Championships and the first qualifier to do so at the US Open since Gilles Müller in 2008.

Seeds
• 🇷🇸 Novak Djokovic (final)

• 🇷🇺 Daniil Medvedev (champion)

• Stefanos Tsitsipas (third round)

• 🇩🇪 Alexander Zverev (semifinals)

• 🇷🇺 Andrey Rublev (third round)

• 🇮🇹 Matteo Berrettini (quarterfinals)

• 🇨🇦 Denis Shapovalov (third round)

• 🇳🇴 Casper Ruud (second round)

• 🇪🇸 Pablo Carreño Busta (first round)

• 🇵🇱 Hubert Hurkacz (second round)

• 🇦🇷 Diego Schwartzman (fourth round)

• 🇨🇦 Félix Auger-Aliassime (semifinals)

• 🇮🇹 Jannik Sinner (fourth round)

• 🇦🇺 Alex de Minaur (first round)

• 🇧🇬 Grigor Dimitrov (second round, retired)

•  Cristian Garín (second round)

• 🇫🇷 Gaël Monfils (third round)

• 🇪🇸 Roberto Bautista Agut (third round)

• 🇺🇸 John Isner (first round)

• 🇮🇹 Lorenzo Sonego (first round)

• 🇷🇺 Aslan Karatsev (third round)

• 🇺🇸 Reilly Opelka (fourth round)

• 🇫🇷 Ugo Humbert (first round)

• 🇬🇧 Daniel Evans (fourth round)

• 🇷🇺 Karen Khachanov (first round)

• 🇬🇧 Cameron Norrie (first round)

• 🇧🇪 David Goffin (first round)

• 🇮🇹 Fabio Fognini (first round)

• 🇪🇸 Alejandro Davidovich Fokina (first round)

•  Marin Čilić (first round, retired)

• 🇰🇿 Alexander Bublik (second round)

• 🇷🇸 Filip Krajinović (first round)

Seeded players
The following are the seeded players. Seedings are based on ATP rankings as of August 23, 2021. Rank and points before are as of August 30, 2021.

As a result of pandemic-related adjustments to the ranking system, players are defending the greater of their points from the 2019 and 2020 tournaments.

† Because the 2020 tournament was non-mandatory, the player was defending 150 points from his 19th best result instead of 90 points from the 2020 US Open.

‡ The player was also defending points from one or more 2019 ATP Challenger Tour tournaments. Those points were frozen in 2020 as a result of pandemic-related adjustments to the ranking system.

§ The player did not qualify for the tournament in 2019 or 2020 and is defending points from a 2020 ATP Challenger Tour tournament (Ostrava) instead.

^ Because the 2021 tournament was non-mandatory, the player substituted his 19th best result in place of the points won in this tournament.

Withdrawn players
The following players would have been seeded, but withdrew before the tournament began.

^ Because the 2021 tournament was non-mandatory, the player substituted his 19th best result in place of zero points for this tournament.

Wild card entries
• 🇺🇸 Jenson Brooksby

• 🇺🇸 Ernesto Escobedo

• 🇺🇸 Brandon Nakashima

• 🇺🇸 Emilio Nava

• 🇦🇺 Max Purcell

• 🇺🇸 Sam Riffice

• 🇺🇸 Jack Sock

• 🇺🇸 Zachary Svajda

Qualifiers
• 🇺🇸 Maxime Cressy

• 🇷🇺 Evgeny Donskoy

• 🇺🇸 Christopher Eubanks

• 🇩🇪 Peter Gojowczyk

• 🇫🇷 Quentin Halys

• 🇫🇷 Antoine Hoang

• 🇹🇷 Cem İlkel

• Ivo Karlović

•  Henri Laaksonen

• 🇵🇱 Kamil Majchrzak

• 🇩🇪 Maximilian Marterer

• 🇸🇰 Alex Molčan

• 🇩🇪 Oscar Otte

•  Holger Rune

• 🇦🇷 Marco Trungelliti

•  Botic van de Zandschulp

Lucky losers
• 🇰🇿 Mikhail Kukushkin

• 🇯🇵 Yūichi Sugita

• 🇪🇸 Bernabé Zapata Miralles

Protected ranking

 * 🇩🇪 Philipp Kohlschreiber (96)

Withdrawals
• Stan Wawrinka (29) → replaced by 🇬🇧 Andy Murray (104)

•  Roger Federer (9) → replaced by  Tallon Griekspoor (105)

•  Borna Ćorić (33) → replaced by 🇺🇸 Mackenzie McDonald (106)

• 🇬🇧 Kyle Edmund (85) → replaced by 🇺🇸 Denis Kudla (107)

• 🇦🇹 Dominic Thiem (6) → replaced by 🇪🇸 Carlos Taberner (108)

• 🇪🇸 Rafael Nadal (3) → replaced by 🇮🇹 Salvatore Caruso (109)

•  Aljaž Bedene (58) → replaced by 🇯🇵 Taro Daniel (110)

• 🇨🇦 Milos Raonic (22)  → replaced by 🇪🇸 Bernabé Zapata Miralles (LL)

• 🇫🇷 Jo-Wilfried Tsonga (93) → replaced by 🇯🇵 Yūichi Sugita (LL)

• 🇫🇷 Gilles Simon (102) → replaced by 🇰🇿 Mikhail Kukushkin (LL)