# 2021 Open Sopra Steria de Lyon – Singles

Corentin Moutet was the defending champion but chose not to defend his title.
Pablo Cuevas won the title after defeating Elias Ymer 6–2, 6–2 in the final.

## Seeds

* Pablo Cuevas (champion)
* Fernando Verdasco (second round)
* Facundo Bagnis (semifinals)
* Daniel Elahi Galán (second round)
* Taro Daniel (semifinals)
* Benjamin Bonzi (first round)
* Francisco Cerúndolo (first round)
* Cedrik-Marcel Stebe (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 | Final | Final | Final | Final |
| 1 | Pablo Cuevas | 6 | 6 | | | | |
| 3 | Facundo Bagnis | 4 | 1 | | | | |
| 3 | Facundo Bagnis | 4 | 1 | 1 | Pablo Cuevas | 6 | 6 |
| | | | | | Elias Ymer | 2 | 2 |
| 5 | Taro Daniel | 4 | 2 | | Elias Ymer | 2 | 2 |
| | Elias Ymer | 6 | 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 | Semifinals |
| 1 | P Cuevas | 4 | 7$^7$ | 6 | | | | | | | | | | | | | |
| Q | P Cachin | 6 | 6$^5$ | 2 | 1 | P Cuevas | 6 | 6 | | | | | | | | | |
| | J Domingues | 3 | 6 | 4 | WC | K Jacquet | 4 | 1 | | | | | | | | | |
| WC | K Jacquet | 6 | 4 | 6 | | | | | | 1 | P Cuevas | 6 | 7 | | | | |
| | A Pellegrino | 6 | 0 | 6 | | | | | | | A Pellegrino | 3 | 5 | | | | |
| Q | C Ugo Carabelli | 4 | 6 | 4 | | A Pellegrino | 7$^8$ | 3 | 6 | | | | | | | | |
| | M Janvier | 6 | 6 | | | M Janvier | 6$^6$ | 6 | 3 | | | | | | | | |
| 7 | F Cerúndolo | 3 | 3 | | | | | | | | | | | 1 | P Cuevas | 6 | 6 |
| 3 | F Bagnis | 5 | 6 | 6 | | | | | | | | | | 3 | F Bagnis | 4 | 1 |
| Q | A Vatutin | 7 | 3 | 2 | 3 | F Bagnis | 6 | 6 | | | | | | | | | |
| | M Trungelliti | 6$^2$ | 2 | | | T Lamasine | 4 | 0 | | | | | | | | | |
| | T Lamasine | 7$^7$ | 6 | | | | | | | 3 | F Bagnis | 6 | 7$^7$ | | | | |
| WC | M Martineau | 4 | 2 | | | | | | | 8 | C-M Stebe | 3 | 6$^5$ | | | | |
| | TM Etcheverry | 6 | 6 | | | TM Etcheverry | 1 | 4 | | | | | | | | | |
| Q | M Guinard | 3 | 3 | | 8 | C-M Stebe | 6 | 6 | | | | | | | | | |
| 8 | C-M Stebe | 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 5 | T Daniel | 6 | 6 | | | | | | | | | | | | | | | |
| | A Collarini | 3 | 2 | | 5 | T Daniel | 6 | 6 | | | | | | | | | | |
| | B Fratangelo | 6 | 6 | | | B Fratangelo | 3 | 4 | | | | | | | | | | |
| LL | M Geerts | 3 | 3 | | | | | | | 5 | T Daniel | 7$^7$ | 6$^2$ | 6 | | | | |
| | D Altmaier | 6 | 6 | | | | | | | | D Altmaier | 6$^3$ | 7$^7$ | 3 | | | | |
| | A Müller | 3 | 2 | | | D Altmaier | 6 | 3 | 7$^8$ | | | | | | | | | |
| LL | L Lokoli | 2$^r$ | | | 4 | DE Galán | 4 | 6 | 6$^6$ | | | | | | | | | |
| 4 | DE Galán | 5 | | | | | | | | | | | | | 5 | T Daniel | 4 | 2 |
| 6 | B Bonzi | 6 | 6$^5$ | 4 | | | | | | | | | | | | E Ymer | 6 | 6 |
| | O Otte | 4 | 7$^7$ | 6 | | O Otte | 4 | 4 | | | | | | | | | | |
| | C Lestienne | 4 | 0$^r$ | | | E Ymer | 6 | 6 | | | | | | | | | | |
| | E Ymer | 6 | 0 | | | | | | | | E Ymer | 6 | 5 | | | | | |
| WC | T Droguet | 6$^3$ | 6 | 4 | | | | | | SE | H Rune | 3 | 3$^r$ | | | | | |
| SE | H Rune | 7$^7$ | 1 | 6 | SE | H Rune | 6 | 6 | | | | | | | | | | |
| | S Nagal | 7$^7$ | 6$^3$ | 5 | 2 | F Verdasco | 4 | 3 | | | | | | | | | | |
| 2 | F Verdasco | 6$^5$ | 7$^7$ | 7 | | | | | | | | | | | | | | |