2021 Erste Bank Open – Singles

Andrey Rublev was the defending champion, but chose to compete in St. Petersburg instead.

Alexander Zverev won the title, defeating Frances Tiafoe in the final, 7–5, 6–4.

Seeds
• # Stefanos Tsitsipas (second round)

• #🇩🇪 Alexander Zverev (champion)

• #🇮🇹 Matteo Berrettini (quarterfinals)

• #🇳🇴 Casper Ruud (quarterfinals)

• #🇵🇱 Hubert Hurkacz (first round)

• #🇨🇦 Félix Auger-Aliassime (quarterfinals)

• #🇮🇹 Jannik Sinner (semifinals)

• #🇦🇷 Diego Schwartzman (quarterfinals)

Seeds
• #🇺🇸 Frances Tiafoe (qualified)

• #🇺🇸 Marcos Giron (first round)

• # Kevin Anderson (qualified)

• #🇩🇪 Dominik Koepfer (qualifying competition, lucky loser)

• #🇮🇹 Gianluca Mager (qualified)

• #🇦🇺 Alexei Popyrin (qualified)

• #🇪🇸 Roberto Carballés Baena (qualifying competition)

• #🇩🇪 Peter Gojowczyk (first round)

Qualifiers
• # 🇺🇸 Frances Tiafoe

• # 🇦🇺 Alexei Popyrin

• # Kevin Anderson

• # 🇮🇹 Gianluca Mager

Lucky loser
• # 🇩🇪 Dominik Koepfer