2021 I.ČLTK Prague Open – Men's singles

The men's singles of the 2021 I.ČLTK Prague Open tournament was played on clay in Prague, Czech Republic.

Stan Wawrinka was the defending champion but chose not to partake in this edition.

Tallon Griekspoor won the title after defeating Oscar Otte 5–7, 6–4, 6–4 in the final.

Seeds
• # 🇸🇰 Norbert Gombos (semifinals)

• # 🇯🇵 Yūichi Sugita (first round, retired)

• # 🇸🇰 Andrej Martin (second round)

• # 🇦🇹 Dennis Novak (first round)

• # 🇺🇸 Denis Kudla (first round)

• # 🇵🇱 Kamil Majchrzak (first round)

• # 🇩🇪 Peter Gojowczyk (first round)

• # 🇮🇳 Sumit Nagal (quarterfinals)