# 2021 Iași Open – Singles

Carlos Taberner was the defending champion but chose not to defend his title.
Zdeněk Kolář won the title after defeating Hugo Gaston 7–5, 4–6, 6–4 in the final.

## Seeds

* Hugo Gaston (final)
* Enzo Couacaud (first round)
* Alexandre Müller (first round)
* Felipe Meligeni Alves (semifinals)
* Zdeněk Kolář (champion)
* Marius Copil (second round)
* Maxime Janvier (first round)
* Dimitar Kuzmanov (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 | Semifinals | Final | Final | Final | Final | Final |
| 1 | Hugo Gaston | 7 | 7$^7$ | | | | | | |
| 4 | Felipe Meligeni Alves | 5 | 6$^4$ | | | | | | |
| 4 | Felipe Meligeni Alves | 5 | 6$^4$ | | 1 | Hugo Gaston | 5 | 6 | 4 |
| | | | | | 5 | Zdeněk Kolář | 7 | 4 | 6 |
| Q | Miljan Zekić | 5 | 6 | 2 | 5 | Zdeněk Kolář | 7 | 4 | 6 |
| 5 | Zdeněk Kolář | 7 | 2 | 6 | | | | | |

### 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 |
| 1 | H Gaston | 6 | 3 | 6 | | | | | | | | | | | | | | |
| | N Fatić | 1 | 6 | 1 | 1 | H Gaston | 4 | 6 | 7$^7$ | | | | | | | | | |
| | M Pecotić | 4 | 6 | 6 | | M Pecotić | 6 | 4 | 6$^5$ | | | | | | | | | |
| | R Ortega Olmedo | 6 | 0 | 1 | | | | | | 1 | H Gaston | 7$^7$ | 6 | | | | | |
| | D Ajduković | 6 | 6 | | | | | | | | D Ajduković | 6$^4$ | 2 | | | | | |
| WC | C Crețu | 3 | 2 | | | D Ajduković | 6 | 6 | | | | | | | | | | |
| Q | A Lazarov | 6 | 3 | 2 | 6 | M Copil | 4 | 4 | | | | | | | | | | |
| 6 | M Copil | 3 | 6 | 6 | | | | | | | | | | | 1 | H Gaston | 7 | 7$^7$ |
| 4 | F Meligeni Alves | 7 | 6 | | | | | | | | | | | | 4 | F Meligeni Alves | 5 | 6$^4$ |
| | I Sijsling | 5 | 2 | | 4 | F Meligeni Alves | 6 | 6 | | | | | | | | | | |
| WC | Ștefan Paloși | 4 | 4 | | PR | M Donati | 3 | 3 | | | | | | | | | | |
| PR | M Donati | 6 | 6 | | | | | | | 4 | F Meligeni Alves | 6 | 3 | 6 | | | | |
| | N Sánchez Izquierdo | 3 | 6 | 2 | | | | | | 8 | D Kuzmanov | 0 | 6 | 3 | | | | |
| WC | ND Ionel | 6 | 4 | 6 | WC | ND Ionel | 6 | 3 | 4 | | | | | | | | | |
| | P Krstin | 2 | 2 | | 8 | D Kuzmanov | 2 | 6 | 6 | | | | | | | | | |
| 8 | D Kuzmanov | 6 | 6 | | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 7 | M Janvier | 3 | 6$^4$ | | | | | | | | | | | | | | |
| Q | M Zekić | 6 | 7$^7$ | | Q | M Zekić | 6 | 7$^7$ | | | | | | | | | |
| Alt | H Casanova | 6 | 6 | | Alt | H Casanova | 3 | 6$^3$ | | | | | | | | | |
| | N Serdarušić | 4 | 4 | | | | | | Q | M Zekić | 7 | 6 | | | | | |
| | T Gabashvili | 5 | 6 | 5 | | | | | | L Miedler | 5 | 2 | | | | | |
| | L Miedler | 7 | 4 | 7 | | L Miedler | 7$^7$ | 6 | | | | | | | | | |
| | A Andreev | 6 | 1 | 6 | | A Andreev | 6$^5$ | 1 | | | | | | | | | |
| 3 | A Müller | 4 | 6 | 3 | | | | | | | | | Q | M Zekić | 5 | 6 | 2 |
| 5 | Z Kolář | 6 | 7 | | | | | | | | | | 5 | Z Kolář | 7 | 2 | 6 |
| Q | David Poljak | 2 | 5 | | 5 | Z Kolář | 6 | 6 | | | | | | | | | |
| | A Dougaz | 6 | 7$^7$ | | | A Dougaz | 2 | 3 | | | | | | | | | |
| LL | B Bobrov | 4 | 6$^4$ | | | | | | 5 | Z Kolář | 6 | 6 | | | | | |
| Q | Dan Alexandru Tomescu | 4 | 3 | | | | | | | R Bonadio | 4 | 4 | | | | | |
| | FC Jianu | 6 | 6 | | | FC Jianu | 6$^5$ | 2 | | | | | | | | | |
| | R Bonadio | 7$^7$ | 6 | | | R Bonadio | 7$^7$ | 6 | | | | | | | | | |
| 2 | E Couacaud | 6$^5$ | 3 | | | | | | | | | | | | | | |