2021 Halle Open – Singles

Ugo Humbert defeated Andrey Rublev in the final 6–3, 7–6(7–4), to win the singles tennis title at the 2021 Halle Open. Humbert's win earned him his third career ATP Tour singles title and his first ATP 500 victory, and also made him the first French player to win the tournament since Henri Leconte won the inaugural edition in 1993. Both Humbert and Rublev were contesting their first career final on grass.

Roger Federer was the defending champion from when the event was last held in 2019, but he lost in the second round to Félix Auger-Aliassime.

Seeds
• #🇷🇺 Daniil Medvedev (first round)

• # Stefanos Tsitsipas (withdrew)

• #🇩🇪 Alexander Zverev (second round)

• #🇷🇺 Andrey Rublev (final)

• # Roger Federer (second round)

• #🇪🇸 Roberto Bautista Agut (first round)

• #🇧🇪 David Goffin (first round, retired)

• #🇫🇷 Gaël Monfils (first round)

Seeds
• # Nikoloz Basilashvili (qualified)

• # 🇧🇾 Egor Gerasimov (first round)

• # 🇺🇸 Marcos Giron (qualified)

• # 🇲🇩 Radu Albot (first round)

• # 🇧🇾 Ilya Ivashka (qualified)

• # 🇱🇹 Ričardas Berankis (qualified)

• # 🇩🇪 Yannick Hanfmann (qualifying competition, lucky loser)

• # 🇦🇺 James Duckworth (qualifying competition)

• # 🇨🇴 Daniel Elahi Galán (qualifying competition)

• # 🇦🇹 Dennis Novak (qualifying competition)

• # João Sousa (qualifying competition)

• # 🇫🇷 Arthur Rinderknech (qualified)

Qualifiers
• # Nikoloz Basilashvili

• # 🇸🇰 Lukáš Lacko

• # 🇺🇸 Marcos Giron

• # 🇫🇷 Arthur Rinderknech

• # 🇧🇾 Ilya Ivashka

• # 🇱🇹 Ričardas Berankis

Lucky loser

 * 1) 🇩🇪 Yannick Hanfmann