# 2021 Open Castilla y León – Singles

Nicola Kuhn was the defending champion but chose not to defend his title.
Benjamin Bonzi won the title after defeating Tim van Rijthoven 7–6$^{(12–10)}$, 3–6, 6–4 in the final.

## Seeds

* Feliciano López (quarterfinals)
* Benjamin Bonzi (champion)
* Grégoire Barrère (withdrew)
* Marc-Andrea Hüsler (first round)
* Frederico Ferreira Silva (first round, retired)
* Quentin Halys (first round)
* Mathias Bourgue (quarterfinals)
* Altuğ Çelikbilek (quarterfinals)
* Cem İlkel (second 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 |
| | Hugo Grenier | 6$^7$ | 2 | | | | | | |
| | Tim van Rijthoven | 7$^9$ | 6 | | | | | | |
| | Tim van Rijthoven | 7$^9$ | 6 | | | Tim van Rijthoven | 6$^{10}$ | 6 | 4 |
| | | | | | 2 | Benjamin Bonzi | 7$^{12}$ | 3 | 6 |
| Q | Nicolas Moreno de Alboran | 3 | 6 | 2 | 2 | Benjamin Bonzi | 7$^{12}$ | 3 | 6 |
| 2 | Benjamin Bonzi | 6 | 4 | 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 | Semifinals | Semifinals | Semifinals |
| 1 | F López | 6 | 7$^7$ | | | | | | | | | | | | | |
| WC | N Sánchez Izquierdo | 4 | 6$^2$ | | 1 | F López | 6$^3$ | 6 | 6 | | | | | | | |
| WC | Julio César Porras | 7$^8$ | 6 | | WC | J César Porras | 7$^7$ | 2 | 4 | | | | | | | |
| | H Moriya | 6$^6$ | 2 | | | | | | | 1 | F López | 6$^6$ | 1 | | | |
| | H Grenier | 6 | 6 | | | | | | | | H Grenier | 7$^8$ | 6 | | | |
| | P Kotov | 4 | 2 | | | H Grenier | 3 | 6 | 6 | | | | | | | |
| Q | C Gimeno Valero | 6 | 7$^7$ | | Q | C Gimeno Valero | 6 | 3 | 2 | | | | | | | |
| 6 | Q Halys | 3 | 6$^3$ | | | | | | | | | | | H Grenier | 6$^7$ | 2 |
| 4 | M-A Hüsler | 7$^8$ | 6$^4$ | 5 | | | | | | | | | | T van Rijthoven | 7$^9$ | 6 |
| | T van Rijthoven | 6$^6$ | 7$^7$ | 7 | | T van Rijthoven | 4 | 6 | 6 | | | | | | | |
| | M Jaziri | 6$^5$ | 6 | 6 | | M Jaziri | 6 | 3 | 3 | | | | | | | |
| | JC Aragone | 7$^7$ | 2 | 1 | | | | | | | T van Rijthoven | 6 | 7$^7$ | | | |
| WC | A Moro Cañas | 3 | 7$^8$ | 6 | | | | | | 7 | M Bourgue | 4 | 6$^3$ | | | |
| | G Oliveira | 6 | 6$^6$ | 1 | WC | A Moro Cañas | 4 | 2 | | | | | | | | |
| Alt | FC Jianu | 3 | 4 | | 7 | M Bourgue | 6 | 6 | | | | | | | | |
| 7 | M Bourgue | 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 | Semifinals |
| 8 | A Çelikbilek | 6 | 6 | | | | | | | | | | | | | | | |
| Alt | J Härteis | 3 | 4 | | 8 | A Çelikbilek | 6 | 3 | 6 | | | | | | | | | |
| | I Sijsling | 1 | 3 | | | T Gabashvili | 3 | 6 | 3 | | | | | | | | | |
| | T Gabashvili | 6 | 6 | | | | | | | 8 | A Çelikbilek | 4 | 2 | | | | | |
| Q | L Vanni | 4 | 3 | | | | | | | Q | N Moreno de Alboran | 6 | 6 | | | | | |
| Q | N Moreno de Alboran | 6 | 6 | | Q | N Moreno de Alboran | 6 | 6 | | | | | | | | | | |
| | R Ortega Olmedo | 6 | 6$^4$ | 4 | 9 | C İlkel | 4 | 0 | | | | | | | | | | |
| 9 | C İlkel | 3 | 7$^7$ | 6 | | | | | | | | | | Q | N Moreno de Alboran | 3 | 6 | 2 |
| 5 | F Ferreira Silva | 4 | 0$^r$ | | | | | | | | | | | 2 | B Bonzi | 6 | 4 | 6 |
| Q | D Svrčina | 6 | 0 | | Q | D Svrčina | 6 | 3 | 6 | | | | | | | | | |
| | R Olivo | 7 | 6 | | | R Olivo | 4 | 6 | 4 | | | | | | | | | |
| | A Menéndez Maceiras | 5 | 2 | | | | | | | Q | D Svrčina | 3 | 4 | | | | | |
| | M Bašić | 4 | 1 | | | | | | | 2 | B Bonzi | 6 | 6 | | | | | |
| | M Viola | 6 | 6 | | | M Viola | 1 | 2 | | | | | | | | | | |
| Alt | A Andreev | 7$^7$ | 4 | 6$^3$ | 2 | B Bonzi | 6 | 6 | | | | | | | | | | |
| 2 | B Bonzi | 6$^2$ | 6 | 7$^7$ | | | | | | | | | | | | | | |