# 2021 Biella Challenger Indoor III – Singles

Kwon Soon-woo was the defending champion but chose not to defend his title.
Andreas Seppi won the title after defeating Liam Broady 6–2, 6–1 in the final.

## Seeds

* James Duckworth (first round)
* Andreas Seppi (champion)
* Yūichi Sugita (first round)
* Yasutaka Uchiyama (first round)
* Peter Gojowczyk (quarterfinals, retired)
* Jurij Rodionov (quarterfinals)
* Marc-Andrea Hüsler (first round)
* Martin Kližan (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 | Final | Final | Final | Final |
| | Illya Marchenko | 3 | 6$^2$ | | | | |
| | Liam Broady | 6 | 7$^7$ | | | | |
| | Liam Broady | 6 | 7$^7$ | | Liam Broady | 2 | 1 |
| | | | | 2 | Andreas Seppi | 6 | 6 |
| | Robin Haase | 1 | 5 | 2 | Andreas Seppi | 6 | 6 |
| 2 | Andreas Seppi | 6 | 7 | | | | |

### 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 | J Duckworth | 4 | 3 | | | | | | | | | | | | | |
| Q | A Arnaboldi | 6 | 6 | | Q | A Arnaboldi | 2 | 5 | | | | | | | | |
| | T-l Wu | 4 | 6$^2$ | | | I Marchenko | 6 | 7 | | | | | | | | |
| | I Marchenko | 6 | 7$^7$ | | | | | | | | I Marchenko | 6 | 6 | | | |
| Q | J Forejtek | 6 | 6 | | | | | | | Q | J Forejtek | 4 | 1 | | | |
| | T Kamke | 3 | 3 | | Q | J Forejtek | 7$^8$ | 6 | | | | | | | | |
| Q | A Santillan | 7 | 3 | 6 | Q | A Santillan | 6$^6$ | 3 | | | | | | | | |
| 7 | M-A Hüsler | 5 | 6 | 3 | | | | | | | | | | I Marchenko | 3 | 6$^2$ |
| 3 | Y Sugita | 2 | 2 | | | | | | | | | | | L Broady | 6 | 7$^7$ |
| WC | L Nardi | 6 | 6 | | WC | L Nardi | 3 | 4 | | | | | | | | |
| | L Broady | 7$^7$ | 6 | | | L Broady | 6 | 6 | | | | | | | | |
| LL | J Lenz | 6$^1$ | 4 | | | | | | | | L Broady | 6 | 6 | | | |
| | Z Kolář | 6 | 7$^7$ | | | | | | | 6 | J Rodionov | 4 | 3 | | | |
| | Y Maden | 2 | 6$^4$ | | | Z Kolář | 2 | 6 | 6$^7$ | | | | | | | |
| | A Vukic | 4 | 4 | | 6 | J Rodionov | 6 | 4 | 7$^9$ | | | | | | | |
| 6 | J Rodionov | 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 |
| 8 | M Kližan | 1 | 1 | | | | | | | | | | | | | | |
| Q | M Bachinger | 6 | 6 | | Q | M Bachinger | 2 | 4 | | | | | | | | | |
| | D Masur | 7$^7$ | 3 | 2 | | R Haase | 6 | 6 | | | | | | | | | |
| | R Haase | 6$^5$ | 6 | 6 | | | | | | | R Haase | 6 | 6 | | | | |
| | B Schnur | 6 | 6 | | | | | | | | B Schnur | 3 | 4 | | | | |
| WC | S Napolitano | 2 | 4 | | | B Schnur | 6 | 6 | | | | | | | | | |
| | L Giustino | 7 | 6 | | | L Giustino | 4 | 2 | | | | | | | | | |
| 4 | Y Uchiyama | 5 | 4 | | | | | | | | | | | | R Haase | 1 | 5 |
| 5 | P Gojowczyk | 6$^5$ | 6 | 6 | | | | | | | | | | 2 | A Seppi | 6 | 7 |
| WC | G Zeppieri | 7$^7$ | 0 | 1 | 5 | P Gojowczyk | 6$^5$ | 6 | 7$^7$ | | | | | | | | |
| PR | D Brown | 1 | 4 | | | Q Halys | 7$^7$ | 1 | 6$^4$ | | | | | | | | |
| | Q Halys | 6 | 6 | | | | | | | 5 | P Gojowczyk | 1$^r$ | | | | | |
| | H Grenier | 4 | 2 | | | | | | | 2 | A Seppi | 3 | | | | | |
| | T Lamasine | 6 | 6 | | | T Lamasine | 6 | 1 | 6$^4$ | | | | | | | | |
| | S Stakhovsky | 2 | 4 | | 2 | A Seppi | 1 | 6 | 7$^7$ | | | | | | | | |
| 2 | A Seppi | 6 | 6 | | | | | | | | | | | | | | |