# 2021 Biella Challenger Indoor IV – Singles

Andreas Seppi was the defending champion but lost in the second round to Matthias Bachinger.
Daniel Masur won the title after defeating Bachinger 6–3, 6–7$^{(8–10)}$, 7–5 in the final.

## Seeds

* Lucas Pouille (second round)
* Yannick Hanfmann (first round)
* Andreas Seppi (second round)
* Yūichi Sugita (first round)
* Yasutaka Uchiyama (first round)
* Ilya Ivashka (first round)
* Grégoire Barrère (quarterfinals)
* Benjamin Bonzi (semifinals)

## 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 | Final |
| | Illya Marchenko | 3 | 3 | | | | | |
| Q | Daniel Masur | 6 | 6 | | | | | |
| Q | Daniel Masur | 6 | 6 | Q | Daniel Masur | 6 | 6$^8$ | 7 |
| | | | | Q | Matthias Bachinger | 3 | 7$^{10}$ | 5 |
| Q | Matthias Bachinger | 7 | 6 | Q | Matthias Bachinger | 3 | 7$^{10}$ | 5 |
| 8 | Benjamin Bonzi | 5 | 4 | | | | | |

### 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 | L Pouille | 6 | 7$^8$ | | | | | | | | | | | | | | |
| Alt | Q Halys | 2 | 6$^6$ | | 1 | L Pouille | 4 | 3 | | | | | | | | | |
| | I Marchenko | 6 | 7 | | | I Marchenko | 6 | 6 | | | | | | | | | |
| WC | F Cobolli | 3 | 5 | | | | | | | | I Marchenko | 7$^{10}$ | 6 | | | | |
| WC | S Napolitano | 6$^5$ | 6 | 4 | | | | | | 7 | G Barrère | 6$^8$ | 1 | | | | |
| Alt | Z Kolář | 7$^7$ | 0 | 6 | Alt | Z Kolář | 2 | 4 | | | | | | | | | |
| | A Vukic | 5 | 6$^5$ | | 7 | G Barrère | 6 | 6 | | | | | | | | | |
| 7 | G Barrère | 7 | 7$^7$ | | | | | | | | | | | | I Marchenko | 3 | 3 |
| 4 | Y Sugita | 6$^4$ | 7$^7$ | 3 | | | | | | | | | | Q | D Masur | 6 | 6 |
| Q | D Masur | 7$^7$ | 6$^3$ | 6 | Q | D Masur | 7 | 6$^4$ | 6 | | | | | | | | |
| Q | J Forejtek | 6 | 6$^2$ | 6 | Q | J Forejtek | 5 | 7$^7$ | 4 | | | | | | | | |
| PR | D Brown | 3 | 7$^7$ | 4 | | | | | | Q | D Masur | 7$^7$ | 6 | | | | |
| | S Stakhovsky | 7 | 5 | 6 | | | | | | | S Stakhovsky | 6$^3$ | 4 | | | | |
| WC | M Gigante | 5 | 7 | 2 | | S Stakhovsky | 7 | 3 | 7$^7$ | | | | | | | | |
| | M-A Hüsler | 6 | 7$^7$ | | | M-A Hüsler | 5 | 6 | 6$^5$ | | | | | | | | |
| 5 | Y Uchiyama | 2 | 6$^3$ | | | | | | | | | | | | | | |

### 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 |
| 6 | I Ivashka | 3 | 7 | 4 | | | | | | | | | | | | |
| | Y Maden | 6 | 5 | 6 | | Y Maden | 3 | 4 | | | | | | | | |
| | S Ofner | 6 | 6 | | | S Ofner | 6 | 6 | | | | | | | | |
| LL | N Kuhn | 2 | 2 | | | | | | | S Ofner | 6$^5$ | 0$^r$ | | | | |
| Q | M Bachinger | 7$^7$ | 2 | 6 | | | | | Q | M Bachinger | 7$^7$ | 1 | | | | |
| Q | A Santillan | 6$^4$ | 6 | 4 | Q | M Bachinger | 6 | 7 | | | | | | | | |
| LL | J Sock | 6 | 3 | 3 | 3 | A Seppi | 3 | 5 | | | | | | | | |
| 3 | A Seppi | 4 | 6 | 6 | | | | | | | | | Q | M Bachinger | 7 | 6 |
| 8 | B Bonzi | 6$^5$ | 6 | 6 | | | | | | | | | 8 | B Bonzi | 5 | 4 |
| | J Rodionov | 7$^7$ | 4 | 4 | 8 | B Bonzi | 7$^7$ | 7$^7$ | | | | | | | | |
| Alt | T Kamke | 6 | 6 | | Alt | T Kamke | 6$^2$ | 6$^3$ | | | | | | | | |
| | E Ymer | 2 | 2 | | | | | | 8 | B Bonzi | 6 | 7$^7$ | | | | |
| | B Tomic | 7$^7$ | 6 | | | | | | | M Bourgue | 3 | 6$^4$ | | | | |
| | R Marcora | 6$^5$ | 1 | | | B Tomic | 3 | 2 | | | | | | | | |
| | M Bourgue | 7 | 4 | 6 | | M Bourgue | 6 | 6 | | | | | | | | |
| 2 | Y Hanfmann | 5 | 6 | 3 | | | | | | | | | | | | |