2021 Sofia Open – Singles

Jannik Sinner was the defending champion and successfully defended his title, defeating Gaël Monfils in the final, 6–3, 6–4.

Seeds
The top four seeds received a bye into the second round. • #🇮🇹 Jannik Sinner (champion)

• #🇫🇷 Gaël Monfils (final)

• #🇦🇺 Alex de Minaur (second round)

• #🇰🇿 Alexander Bublik (withdrew)

• #🇷🇸 Filip Krajinović (semifinals)

• #🇫🇷 Adrian Mannarino (first round)

• #🇪🇸 Alejandro Davidovich Fokina (first round)

• #🇦🇺 John Millman (quarterfinals)

Seeds
• # 🇪🇸 Pedro Martínez (qualified)

• # 🇮🇹 Marco Cecchinato (first round)

• # 🇮🇹 Andreas Seppi (qualified)

• # 🇧🇾 Egor Gerasimov (qualified)

• # 🇨🇴 Daniel Elahi Galán (first round)

• # 🇵🇱 Kamil Majchrzak (qualifying competition, lucky loser)

• # 🇨🇿 Tomáš Macháč (qualifying competition)

• # 🇦🇹 Jurij Rodionov (first round)

Qualifiers
• # 🇪🇸 Pedro Martínez

• # 🇺🇦 Illya Marchenko

• # 🇮🇹 Andreas Seppi

• # 🇧🇾 Egor Gerasimov

Lucky loser
• # 🇵🇱 Kamil Majchrzak