2021 Sparkassen Open – Singles

Thiago Monteiro was the defending champion but chose not to defend his title.

Daniel Altmaier won the title after defeating Henri Laaksonen 6–1, 6–2 in the final.

Seeds
• # 🇫🇷 Benoît Paire (second round)

• # 🇱🇹 Ričardas Berankis (withdrew)

• # 🇩🇪 Yannick Hanfmann (second round)

• # 🇸🇰 Jozef Kovalík (quarterfinals)

• # Henri Laaksonen (final)

• # 🇨🇿 Tomáš Macháč (second round)

• # 🇮🇳 Sumit Nagal (second round)

• # 🇩🇪 Daniel Altmaier (champion)