2021 Sofia Open

The 2021 Sofia Open was a men's tennis tournament played on indoor hard courts. It was the sixth edition of the Sofia Open as part of the ATP World Tour 250 series of the 2021 ATP Tour. It was played at the Arena Armeec in Sofia, Bulgaria, from 27 September to 3 October 2021. First-seeded Jannik Sinner won the singles title.

Singles

 * 🇮🇹 Jannik Sinner defeated 🇫🇷 Gaël Monfils 6–3, 6–4

Doubles

 * 🇬🇧 Jonny O'Mara / 🇬🇧 Ken Skupski defeated 🇦🇹 Oliver Marach / 🇦🇹 Philipp Oswald, 6–3, 6–4

Seeds

 * 1 Rankings are as of 20 September 2021.

Other entrants
The following players received wildcards into the main draw:
 * 🇧🇬 Adrian Andreev
 * 🇧🇬 Dimitar Kuzmanov
 * 🇧🇬 Alexandar Lazarov

The following players received entry from the qualifying draw:
 * 🇧🇾 Egor Gerasimov
 * 🇺🇦 Illya Marchenko
 * 🇪🇸 Pedro Martínez
 * 🇮🇹 Andreas Seppi

The following player received entry as a lucky loser:
 * 🇵🇱 Kamil Majchrzak

Withdrawals

 * Before the tournament
 * 🇪🇸 Roberto Bautista Agut → replaced by 🇦🇺 James Duckworth
 * 🇰🇿 Alexander Bublik → replaced by 🇵🇱 Kamil Majchrzak
 * Marin Čilić → replaced by 🇮🇹 Gianluca Mager
 * 🇺🇸 Mackenzie McDonald → replaced by 🇫🇮 Emil Ruusuvuori


 * During the tournament
 * 🇧🇾 Ilya Ivashka

Seeds

 * 1 Rankings are as of 20 September 2021.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇧🇬 Adrian Andreev / 🇧🇬 Alexandar Lazarov
 * 🇧🇬 Alexander Donski / 🇧🇬 Dimitar Kuzmanov

The following pair received entry as alternates:
 * 🇧🇬 Plamen Milushev / 🇧🇬 Radoslav Shandarov

Withdrawals

 * Before the tournament
 * 🇫🇷 Jérémy Chardy / Hugo Nys → replaced by 🇸🇪 André Göransson /  Hugo Nys
 * 🇦🇺 Matthew Ebden / 🇮🇱 Jonathan Erlich → replaced by 🇮🇱 Jonathan Erlich / 🇬🇧 Dominic Inglot
 * 🇧🇪 Sander Gillé / 🇧🇪 Joran Vliegen → replaced by 🇬🇧 Jonny O'Mara / 🇬🇧 Ken Skupski
 * 🇺🇸 Marcos Giron / 🇺🇸 Mackenzie McDonald → replaced by 🇮🇹 Lorenzo Musetti / 🇮🇹 Andrea Vavassori
 * 🇪🇸 Pedro Martínez / 🇪🇸 Jaume Munar → replaced by 🇧🇬 Plamen Milushev / 🇧🇬 Radoslav Shandarov