2021 Citi Open – Singles

Jannik Sinner defeated Mackenzie McDonald in the final, 7–5, 4–6, 7–5 to win the singles tennis title at the 2021 Citi Open. With the victory, Sinner became the youngest player and first teenager on the ATP Tour to win an ATP 500 title since the category was created in 2009.

Nick Kyrgios was the reigning champion from when the tournament was last held in 2019, but lost in the first round to McDonald.

Seeds
All seeds receive a bye into the second round. • 🇪🇸 Rafael Nadal (third round)

• 🇨🇦 Félix Auger-Aliassime (third round)

• 🇦🇺 Alex de Minaur (second round)

• 🇧🇬 Grigor Dimitrov (second round)

• 🇮🇹 Jannik Sinner (champion)

• 🇬🇧 Dan Evans (second round)

• 🇬🇧 Cameron Norrie (third round)

• 🇺🇸 Reilly Opelka (third round)

• 🇰🇿 Alexander Bublik (second round)

• 🇺🇸 Taylor Fritz (second round)

• 🇦🇺 John Millman (quarterfinals)

• 🇺🇸 Sebastian Korda (third round)

• 🇫🇷 Benoît Paire (second round)

• Lloyd Harris (quarterfinals)

• 🇷🇸 Miomir Kecmanović (second round)

• 🇺🇸 Frances Tiafoe (second round)

Seeds
• # 🇯🇵 Yasutaka Uchiyama (moved to the main draw)

• # 🇬🇧 Liam Broady (qualifying competition)

• # 🇺🇸 J. J. Wolf (qualifying competition)

• # 🇺🇸 Maxime Cressy (qualifying competition)

• # 🇷🇺 Evgeny Donskoy (first round)

• # 🇮🇳 Prajnesh Gunneswaran (qualified)

• # 🇺🇦 Illya Marchenko (qualified)

• # Jason Jung (first round)

• # 🇦🇹 Sebastian Ofner (qualifying competition)

• # 🇪🇨 Emilio Gómez (qualified)

• # 🇸🇪 Elias Ymer (qualified)

• # 🇺🇸 Mitchell Krueger (qualified)

Qualifiers
• # 🇮🇳 Ramkumar Ramanathan

• # 🇪🇨 Emilio Gómez

• # 🇸🇪 Elias Ymer

• # 🇺🇦 Illya Marchenko

• # 🇺🇸 Mitchell Krueger

• # 🇮🇳 Prajnesh Gunneswaran