# 2021 Bucharest Challenger – Singles

This was the first edition of the tournament.
Jiří Lehečka won the title after defeating Filip Horanský 6–3, 6–2 in the final.

## Seeds

* Stefano Travaglia (semifinals)
* Radu Albot (second round)
* Thanasi Kokkinakis (quarterfinals)
* Zdeněk Kolář (first round)
* Sumit Nagal (first round)
* Maximilian Marterer (second round)
* Vít Kopřiva (second round)
* Jiří Lehečka (champion)

## 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 |
| 1 | Stefano Travaglia | 3 | 6$^3$ | | | | | |
| 8 | Jiří Lehečka | 6 | 7$^7$ | | | | | |
| 8 | Jiří Lehečka | 6 | 7$^7$ | | 8 | Jiří Lehečka | 6 | 6 |
| | | | | | | Filip Horanský | 3 | 2 |
| | Filip Horanský | 6 | 4 | 6 | | Filip Horanský | 3 | 2 |
| | Lorenzo Giustino | 3 | 6 | 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 | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | S Travaglia | 6 | 6 | | | | | | | | | | | | | | |
| | L Rosol | 4 | 3 | | 1 | S Travaglia | 2 | 6 | 6 | | | | | | | | |
| | F Cobolli | 7 | 6$^6$ | 6 | | F Cobolli | 6 | 4 | 2 | | | | | | | | |
| Q | I Gakhov | 5 | 7$^8$ | 1 | | | | | | 1 | S Travaglia | 6 | 6 | | | | |
| | V Sachko | 6 | 6 | | | | | | | | V Sachko | 3 | 4 | | | | |
| | A Erler | 2 | 2 | | | V Sachko | 6 | 2 | 7$^7$ | | | | | | | | |
| | L Miedler | 3 | 1 | | 6 | M Marterer | 3 | 6 | 6$^0$ | | | | | | | | |
| 6 | M Marterer | 6 | 6 | | | | | | | | | | | 1 | S Travaglia | 3 | 6$^3$ |
| 4 | Z Kolář | 5 | 4 | | | | | | | | | | | 8 | J Lehečka | 6 | 7$^7$ |
| | T Gabashvili | 7 | 6 | | | T Gabashvili | 3 | 3 | | | | | | | | | |
| WC | ND Ionel | 7$^7$ | 6 | | WC | ND Ionel | 6 | 6 | | | | | | | | | |
| WC | Ștefan Paloși | 6$^5$ | 1 | | | | | | | WC | ND Ionel | 4 | 4 | | | | |
| Q | DN Mădăraș | 6 | 6 | | | | | | | 8 | J Lehečka | 6 | 6 | | | | |
| Alt | FC Jianu | 4 | 3 | | Q | DN Mădăraș | 1 | 2 | | | | | | | | | |
| Alt | A Vatutin | 3 | 1 | | 8 | J Lehečka | 6 | 6 | | | | | | | | | |
| 8 | J Lehečka | 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 7 | V Kopřiva | 6 | 6 | | | | | | | | | | | | | | | |
| | M Copil | 4 | 4 | | 7 | V Kopřiva | 3 | 4 | | | | | | | | | | |
| WC | N Frunză | 6$^3$ | 4 | | | F Horanský | 6 | 6 | | | | | | | | | | |
| | F Horanský | 7$^7$ | 6 | | | | | | | | F Horanský | 7$^7$ | 4 | 6 | | | | |
| Q | C Hemery | 6 | 6 | | | | | | | 3 | T Kokkinakis | 6$^5$ | 6 | 2 | | | | |
| | J Sels | 4 | 4 | | Q | C Hemery | 6 | 6$^4$ | 6$^4$ | | | | | | | | | |
| | D Ajduković | 1 | 1$^r$ | | 3 | T Kokkinakis | 2 | 7$^7$ | 7$^7$ | | | | | | | | | |
| 3 | T Kokkinakis | 6 | 3 | | | | | | | | | | | | F Horanský | 6 | 4 | 6 |
| 5 | S Nagal | 6 | 5 | 5 | | | | | | | | | | | L Giustino | 3 | 6 | 2 |
| | L Giustino | 3 | 7 | 7 | | L Giustino | 2 | 7 | 6 | | | | | | | | | |
| | G Blancaneaux | 4 | 5 | | Q | M Arnaldi | 6 | 5 | 4 | | | | | | | | | |
| Q | M Arnaldi | 6 | 7 | | | | | | | | L Giustino | 6 | 6 | | | | | |
| | R Bonadio | 6$^5$ | 7$^7$ | 6 | | | | | | | R Bonadio | 2 | 3 | | | | | |
| | J Clarke | 7$^7$ | 6$^4$ | 2 | | R Bonadio | 6 | 6 | | | | | | | | | | |
| | N Serdarušić | 2 | 5 | | 2 | R Albot | 3 | 3 | | | | | | | | | | |
| 2 | R Albot | 6 | 7 | | | | | | | | | | | | | | | |