2021 Slovak Open II – Singles

Maximilian Marterer was the defending champion but lost in the quarterfinals to Stefano Travaglia.

Tallon Griekspoor won the title after defeating Zsombor Piros 6–3, 6–2 in the final.

Seeds
• # 🇮🇹 Stefano Travaglia (semifinals, retired)

• # Tallon Griekspoor (champion)

• # 🇪🇸 Carlos Taberner (first round)

• # 🇸🇰 Norbert Gombos (first round)

• # 🇸🇰 Alex Molčan (semifinals)

• # 🇫🇷 Gilles Simon (withdrew)

• # 🇬🇧 Liam Broady (second round)

• # 🇨🇿 Tomáš Macháč (first round)