# 2021 Challenger de Santiago II – Singles

Sebastián Báez was the defending champion but lost in the final to Juan Pablo Varillas.
Varillas won the title after defeating Báez 6–4, 7–5 in the final.

## Seeds

* Juan Manuel Cerúndolo (first round)
* Francisco Cerúndolo (semifinals)
* Juan Pablo Varillas (champion)
* Hugo Dellien (quarterfinals)
* Sebastián Báez (final)
* Marcelo Tomás Barrios Vera (first round)
* Juan Ignacio Londero (first round)
* Felipe Meligeni Alves (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 |
| 5 | Sebastián Báez | 6 | 6 | | | | | |
| | Nicolás Jarry | 4 | 4 | | | | | |
| | Nicolás Jarry | 4 | 4 | | 5 | Sebastián Báez | 4 | 5 |
| | | | | | 3 | Juan Pablo Varillas | 6 | 7 |
| 3 | Juan Pablo Varillas | 6 | 6$^8$ | 6 | 3 | Juan Pablo Varillas | 6 | 7 |
| 2 | Francisco Cerúndolo | 3 | 7$^{10}$ | 3 | | | | |

### 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 | JM Cerúndolo | 0 | 1 | | | | | | | | | | | | | | |
| | N Kicker | 6 | 6 | | | N Kicker | 4 | 4 | | | | | | | | | |
| | R Cid Subervi | 4 | 7$^7$ | 5 | | F Mena | 6 | 6 | | | | | | | | | |
| | F Mena | 6 | 6$^2$ | 7 | | | | | | | F Mena | 3 | 1 | | | | |
| WC | D Fernández Flores | 3 | 6 | 5 | | | | | | 5 | S Báez | 6 | 6 | | | | |
| Alt | N Chappell | 6 | 3 | 7 | Alt | N Chappell | 7 | 4 | 1 | | | | | | | | |
| | D Svrčina | 2 | 5 | | 5 | S Báez | 5 | 6 | 6 | | | | | | | | |
| 5 | S Báez | 6 | 7 | | | | | | | | | | | 5 | S Báez | 6 | 6 |
| 4 | H Dellien | 4 | 6 | 6 | | | | | | | | | | | N Jarry | 4 | 4 |
| Alt | L Catarina | 6 | 3 | 3 | 4 | H Dellien | 6 | 4 | 6 | | | | | | | | |
| Q | N Álvarez | 5 | 1 | | | C Ugo Carabelli | 2 | 6 | 2 | | | | | | | | |
| | C Ugo Carabelli | 7 | 6 | | | | | | | 4 | H Dellien | 6$^4$ | 4 | | | | |
| | N Jarry | 6 | 6 | | | | | | | | N Jarry | 7$^7$ | 6 | | | | |
| | JP Ficovich | 4 | 4 | | | N Jarry | 6$^4$ | 7 | 6 | | | | | | | | |
| Q | F Díaz Acosta | 6 | 5 | 6 | Q | F Díaz Acosta | 7$^7$ | 5 | 4 | | | | | | | | |
| 6 | MT Barrios Vera | 3 | 7 | 1 | | | | | | | | | | | | | |

### 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 |
| 7 | JI Londero | 2 | 3 | | | | | | | | | | | | | | | |
| | TA Tirante | 6 | 6 | | | TA Tirante | 4 | 2 | | | | | | | | | | |
| PR | G Melzer | 6 | 6 | | PR | G Melzer | 6 | 6 | | | | | | | | | | |
| | G Andreozzi | 2 | 4 | | | | | | | PR | G Melzer | 1 | 3 | | | | | |
| WC | Víctor Núñez | 0 | 2 | | | | | | | 3 | JP Varillas | 6 | 6 | | | | | |
| | J Lenz | 6 | 6 | | | J Lenz | 2 | 4 | | | | | | | | | | |
| Alt | H Casanova | 6$^8$ | 6$^7$ | | 3 | JP Varillas | 6 | 6 | | | | | | | | | | |
| 3 | JP Varillas | 7$^{10}$ | 7$^9$ | | | | | | | | | | | 3 | JP Varillas | 6 | 6$^8$ | 6 |
| 8 | F Meligeni Alves | 6 | 3 | 4 | | | | | | | | | | 2 | F Cerúndolo | 3 | 7$^{10}$ | 3 |
| WC | G Lama | 4 | 6 | 6 | WC | G Lama | 6 | 3 | 7 | | | | | | | | | |
| PR | G Oliveira | 6 | 6 | | PR | G Oliveira | 4 | 6 | 5 | | | | | | | | | |
| Q | O Crawford | 4 | 2 | | | | | | | WC | G Lama | 6$^6$ | 4 | | | | | |
| | M Pucinelli de Almeida | 6 | 1 | 3 | | | | | | 2 | F Cerúndolo | 7$^8$ | 6 | | | | | |
| Q | Alexis Gautier | 4 | 6 | 6 | Q | A Gautier | 4 | 2 | | | | | | | | | | |
| LL | C Rodríguez | 3 | 6 | 2 | 2 | F Cerúndolo | 6 | 6 | | | | | | | | | | |
| 2 | F Cerúndolo | 6 | 3 | 6 | | | | | | | | | | | | | | |