# 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)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | Jannik Sinner | 6 | 7 | | | | |
| 5 | Filip Krajinović | 3 | 5 | | | | |
| 5 | Filip Krajinović | 3 | 5 | 1 | Jannik Sinner | 6 | 6 |
| | | | | 2 | Gaël Monfils | 3 | 4 |
| | Marcos Giron | 5 | 0 | 2 | Gaël Monfils | 3 | 4 |
| 2 | Gaël Monfils | 7 | 6 | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| | | | | | 1 | J Sinner | 6 | 7$^7$ | | | | | | | | | |
| Q | E Gerasimov | 5 | 7$^{10}$ | 6 | Q | E Gerasimov | 2 | 6$^3$ | | | | | | | | | |
| | V Pospisil | 7 | 6$^8$ | 3 | | | | | 1 | J Sinner | 7$^7$ | 6 | | | | | |
| | E Ruusuvuori | 6 | 4 | 4 | | | | | | J Duckworth | 6$^4$ | 4 | | | | | |
| | J Duckworth | 3 | 6 | 6 | | J Duckworth | 6 | 6 | | | | | | | | | |
| | B Paire | 6 | 7 | | | B Paire | 4 | 4 | | | | | | | | | |
| 7 | A Davidovich Fokina | 4 | 5 | | | | | | | | | | | 1 | J Sinner | 6 | 7 |
| | | | | | | | | | | | | | | 5 | F Krajinović | 3 | 5 |
| | | | | | LL | K Majchrzak | 7 | 6 | | | | | | | | | |
| WC | D Kuzmanov | 6$^4$ | 7$^7$ | 6 | WC | D Kuzmanov | 5 | 1 | | | | | | | | | |
| | L Musetti | 7$^7$ | 6$^3$ | 3 | | | | | LL | K Majchrzak | 3 | 6 | 3 | | | | |
| Q | P Martínez | 6$^5$ | 3 | | | | | | 5 | F Krajinović | 6 | 4 | 6 | | | | |
| | L Đere | 7$^7$ | 6 | | | L Đere | 3 | 0 | | | | | | | | | |
| WC | A Lazarov | 0 | 3 | | 5 | F Krajinović | 6 | 6 | | | | | | | | | |
| 5 | F Krajinović | 6 | 6 | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 8 | J Millman | 6 | 6 | | | | | | | | | | | | | | |
| | M Ymer | 2 | 4 | | 8 | J Millman | 5 | 7$^7$ | 6 | | | | | | | | |
| Q | A Seppi | 4 | 2 | | Q | I Marchenko | 7 | 6$^0$ | 3 | | | | | | | | |
| Q | I Marchenko | 6 | 6 | | | | | | | 8 | J Millman | 4 | 2 | | | | |
| | J Munar | 7$^7$ | 1 | 4 | | | | | | | M Giron | 6 | 6 | | | | |
| | M Giron | 6$^2$ | 6 | 6 | | M Giron | 7$^7$ | 7$^7$ | | | | | | | | | |
| | | | | | 3 | A de Minaur | 6$^5$ | 6$^2$ | | | | | | | | | |
| | | | | | | | | | | | | | | | M Giron | 5 | 0 |
| 6 | A Mannarino | 3 | 2 | | | | | | | | | | | 2 | G Monfils | 7 | 6 |
| | G Mager | 6 | 6 | | | G Mager | 7$^7$ | 6 | | | | | | | | | |
| | M Kecmanović | 7$^9$ | 6 | | | M Kecmanović | 6$^3$ | 3 | | | | | | | | | |
| WC | A Andreev | 6$^7$ | 4 | | | | | | | | G Mager | 2 | 2 | | | | |
| | I Ivashka | 6 | 6 | | | | | | | 2 | G Monfils | 6 | 6 | | | | |
| | P Andújar | 4 | 3 | | | I Ivashka | | | | | | | | | | | |
| | | | | | 2 | G Monfils | w/o | | | | | | | | | | |

## Qualifying
### 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

### Qualifying draw
#### First qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 1 | Pedro Martínez | 7 | 6 | | | | | |
| WC | Simon Anthony Ivanov | 5 | 1 | | | | | |
| WC | Simon Anthony Ivanov | 5 | 1 | | 1 | Pedro Martínez | 6 | 7$^7$ |
| | | | | | 6 | Kamil Majchrzak | 4 | 6$^4$ |
| | Maxime Cressy | 6 | 4 | 3 | 6 | Kamil Majchrzak | 4 | 6$^4$ |
| 6 | Kamil Majchrzak | 4 | 6 | 6 | | | | |

#### Second qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Marco Cecchinato | 3 | 3 | | | | | |
| | Illya Marchenko | 6 | 6 | | | | | |
| | Illya Marchenko | 6 | 6 | | Illya Marchenko | 3 | 6 | 7$^7$ |
| | | | | 7 | Tomáš Macháč | 6 | 3 | 6$^2$ |
| | Kacper Żuk | 4 | 2 | 7 | Tomáš Macháč | 6 | 3 | 6$^2$ |
| 7 | Tomáš Macháč | 6 | 6 | | | | | |

#### Third qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Andreas Seppi | 7$^7$ | 6 | | | | | |
| | Cem İlkel | 6$^3$ | 2 | | | | | |
| | Cem İlkel | 6$^3$ | 2 | | 3 | Andreas Seppi | 6 | 6 |
| | | | | | WC | Alexander Donski | 3 | 2 |
| WC | Alexander Donski | 2 | 6 | 7$^7$ | WC | Alexander Donski | 3 | 2 |
| 8 | Jurij Rodionov | 6 | 1 | 6$^4$ | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Egor Gerasimov | 6 | 7$^7$ | | | | | |
| | Evgeny Donskoy | 3 | 6$^4$ | | | | | |
| | Evgeny Donskoy | 3 | 6$^4$ | | 4 | Egor Gerasimov | 7$^8$ | 6 |
| | | | | | | Altuğ Çelikbilek | 6$^6$ | 3 |
| | Altuğ Çelikbilek | 7$^8$ | 4 | 7 | | Altuğ Çelikbilek | 6$^6$ | 3 |
| 5 | Daniel Elahi Galán | 6$^6$ | 6 | 5 | | | | |