# 2021 Saint Petersburg Challenger – Singles

This was the first edition of the tournament.
Zizou Bergs won the title after defeating Altuğ Çelikbilek 6–4, 3–6, 6–4 in the final.

## Seeds

* Roman Safiullin (first round)
* Cem İlkel (quarterfinals)
* Rudolf Molleker (first round)
* Christopher Eubanks (first round)
* Teymuraz Gabashvili (first round)
* Alexey Vatutin (second round)
* Roberto Quiroz (second round)
* Evgeny Karlovskiy (first round)

## 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 | Semifinals | Final | Final | Final | Final | Final |
| | Altuğ Çelikbilek | 5 | 6 | 6 | | | | | |
| Q | Artem Dubrivnyy | 7 | 2 | 3 | | | | | |
| Q | Artem Dubrivnyy | 7 | 2 | 3 | | Altuğ Çelikbilek | 4 | 6 | 4 |
| | | | | | Q | Zizou Bergs | 6 | 3 | 6 |
| Q | Zizou Bergs | 7$^9$ | 6 | | Q | Zizou Bergs | 6 | 3 | 6 |
| | Vít Kopřiva | 6$^7$ | 2 | | | | | | |

### Top 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | R Safiullin | 5 | 4 | | | | | | | | | | | | | | | | |
| WC | E Tiurnev | 7 | 6 | | WC | E Tiurnev | 3 | 3 | | | | | | | | | | | |
| | J de Jong | 6 | 4 | 6 | | J de Jong | 6 | 6 | | | | | | | | | | | |
| | U Ignatik | 4 | 6 | 3 | | | | | | | J de Jong | 6$^7$ | 0 | | | | | | |
| | A Çelikbilek | 6 | 6 | | | | | | | | A Çelikbilek | 7$^9$ | 6 | | | | | | |
| | K Sultanov | 4 | 1 | | | A Çelikbilek | 6 | 7$^7$ | | | | | | | | | | | |
| | N Serdarušić | 4 | 6 | 0 | 6 | A Vatutin | 3 | 6$^3$ | | | | | | | | | | | |
| 6 | A Vatutin | 6 | 3 | 6 | | | | | | | | | | | | A Çelikbilek | 5 | 6 | 6 |
| 3 | R Molleker | 6$^2$ | 4 | | | | | | | | | | | | Q | A Dubrivnyy | 7 | 2 | 3 |
| | V Durasovic | 7$^7$ | 6 | | | V Durasovic | 5 | 6 | 3 | | | | | | | | | | |
| | I Sijsling | 6 | 4 | 3 | Q | A Dubrivnyy | 7 | 3 | 6 | | | | | | | | | | |
| Q | A Dubrivnyy | 3 | 6 | 6 | | | | | | Q | A Dubrivnyy | 6 | 6$^8$ | 6 | | | | | |
| | M Pecotić | 6$^0$ | 2 | | | | | | | Q | A Kuznetsov | 3 | 7$^{10}$ | 3 | | | | | |
| Q | A Kuznetsov | 7$^7$ | 6 | | Q | A Kuznetsov | 6 | 6 | | | | | | | | | | | |
| | M Bašić | 6 | 6 | | | M Bašić | 1 | 1 | | | | | | | | | | | |
| 8 | E Karlovskiy | 0 | 4 | | | | | | | | | | | | | | | | |

### 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 |
| 5 | T Gabashvili | 4 | 2 | | | | | | | | | | | | | | |
| | P Kotov | 6 | 6 | | | P Kotov | 0 | 5 | | | | | | | | | |
| Q | Z Bergs | 6 | 6 | | Q | Z Bergs | 6 | 7 | | | | | | | | | |
| | H Bourchier | 4 | 2 | | | | | | | Q | Z Bergs | 6 | 6 | | | | |
| | M Ebden | 6 | 6 | | | | | | | Q | L Catarina | 3 | 4 | | | | |
| | P Krstin | 1 | 4 | | | M Ebden | 6$^4$ | 2 | | | | | | | | | |
| Q | L Catarina | 7 | 6 | | Q | L Catarina | 7$^7$ | 6 | | | | | | | | | |
| 4 | C Eubanks | 5 | 2 | | | | | | | | | | | Q | Z Bergs | 7$^9$ | 6 |
| 7 | R Quiroz | 6 | 6 | | | | | | | | | | | | V Kopřiva | 6$^7$ | 2 |
| | D-h Lee | 2 | 2 | | 7 | R Quiroz | 2 | 4 | | | | | | | | | |
| WC | I Gakhov | 5 | 6 | 6$^7$ | | V Kopřiva | 6 | 6 | | | | | | | | | |
| | V Kopřiva | 7 | 1 | 7$^9$ | | | | | | | V Kopřiva | 7 | 6 | | | | |
| WC | D Stricker | 5 | 6 | 6 | | | | | | 2 | C İlkel | 5 | 2 | | | | |
| | D Ajduković | 7 | 4 | 2 | WC | D Stricker | 7$^7$ | 3 | 3 | | | | | | | | |
| | Shuichi Sekiguchi | 3 | 2 | | 2 | C İlkel | 6$^5$ | 6 | 6 | | | | | | | | |
| 2 | C İlkel | 6 | 6 | | | | | | | | | | | | | | |