2021 Sánchez-Casal Cup – Singles

Carlos Alcaraz was the defending champion but chose not to defend his title.

Dimitar Kuzmanov won the title after defeating Hugo Gaston 6–3, 6–0 in the final.

Seeds
• # 🇫🇷 Hugo Gaston (final)

• # 🇸🇰 Alex Molčan (semifinals)

• # 🇪🇸 Bernabé Zapata Miralles (first round, retired)

• # 🇧🇦 Damir Džumhur (second round)

• # 🇷🇸 Nikola Milojević (second round)

• # 🇦🇺 Marc Polmans (first round)

• # 🇩🇪 Cedrik-Marcel Stebe (withdrew)

• # 🇨🇿 Jiří Lehečka (first round)