# 2021 Open de Rennes – Singles

Arthur Rinderknech was the defending champion but lost in the semifinals to Benjamin Bonzi.
Bonzi won the title after defeating Mats Moraing 7–6$^{(7–3)}$, 7–6$^{(7–3)}$ in the final.

## Seeds

* Richard Gasquet (semifinals)
* Arthur Rinderknech (semifinals)
* Benjamin Bonzi (champion)
* Gilles Simon (first round)
* Andy Murray (second round)
* Lucas Pouille (quarterfinals)
* Grégoire Barrère (second round)
* Tomáš Macháč (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 |
| 1 | Richard Gasquet | 4 | 7 | 2 | | | | |
| | Mats Moraing | 6 | 5 | 6 | | | | |
| | Mats Moraing | 6 | 5 | 6 | | Mats Moraing | 6$^3$ | 6$^3$ |
| | | | | | 3 | Benjamin Bonzi | 7$^7$ | 7$^7$ |
| 3 | Benjamin Bonzi | 6$^9$ | 7$^7$ | 6 | 3 | Benjamin Bonzi | 7$^7$ | 7$^7$ |
| 2 | Arthur Rinderknech | 7$^{11}$ | 6$^4$ | 1 | | | | |

### 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 | Semifinals |
| 1 | R Gasquet | 7$^7$ | 6 | | | | | | | | | | | | | | | |
| WC | K Jacquet | 6$^4$ | 3 | | 1 | R Gasquet | 6 | 6 | | | | | | | | | | |
| | B Schnur | 4 | 4 | | Q | C Chidekh | 1 | 4 | | | | | | | | | | |
| Q | C Chidekh | 6 | 6 | | | | | | | 1 | R Gasquet | 7$^8$ | 7 | | | | | |
| Q | M Guinard | 4 | 3 | | | | | | | | R Safiullin | 6$^6$ | 5 | | | | | |
| | R Safiullin | 6 | 6 | | | R Safiullin | 6 | 4 | 6 | | | | | | | | | |
| | Y Maden | 3 | 1 | | 5/WC | A Murray | 2 | 6 | 1 | | | | | | | | | |
| 5/WC | A Murray | 6 | 6 | | | | | | | | | | | 1 | R Gasquet | 4 | 7 | 2 |
| 4 | G Simon | 3 | 2 | | | | | | | | | | | | M Moraing | 6 | 5 | 6 |
| Alt | T Gabashvili | 6 | 6 | | Alt | T Gabashvili | 4 | 6 | 6 | | | | | | | | | |
| | E Escobedo | 7 | 6 | | | E Escobedo | 6 | 2 | 3 | | | | | | | | | |
| | C Lestienne | 5 | 1 | | | | | | | Alt | T Gabashvili | 2 | 6$^3$ | | | | | |
| | M Moraing | 4 | 7 | 6 | | | | | | | M Moraing | 6 | 7$^7$ | | | | | |
| WC | H Mayot | 6 | 5 | 2 | | M Moraing | 7$^{11}$ | 6 | | | | | | | | | | |
| Q | C Hemery | 1 | 1 | | 8 | T Macháč | 6$^9$ | 1 | | | | | | | | | | |
| 8 | T Macháč | 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 |
| 7 | G Barrère | 7$^9$ | 7 | | | | | | | | | | | | | | | |
| | T van Rijthoven | 6$^7$ | 5 | | 7 | G Barrère | 6$^7$ | 6 | 4 | | | | | | | | | |
| Q | A Bega | 2 | 1 | | | L Broady | 7$^9$ | 4 | 6 | | | | | | | | | |
| | L Broady | 6 | 6 | | | | | | | | L Broady | 4 | 2 | | | | | |
| | K Żuk | 7 | 6 | | | | | | | 3 | B Bonzi | 6 | 6 | | | | | |
| LL | M Rosenkranz | 5 | 3 | | | K Żuk | 6$^3$ | 3 | | | | | | | | | | |
| | E Ymer | 3 | 4 | | 3 | B Bonzi | 7$^7$ | 6 | | | | | | | | | | |
| 3 | B Bonzi | 6 | 6 | | | | | | | | | | | 3 | B Bonzi | 6$^9$ | 7$^7$ | 6 |
| 6 | L Pouille | 5 | 6 | 6 | | | | | | | | | | 2 | A Rinderknech | 7$^{11}$ | 6$^4$ | 1 |
| | M Janvier | 7 | 4 | 3 | 6 | L Pouille | 3 | 6 | 6 | | | | | | | | | |
| LL | D Added | 3 | 4 | | | A Hoang | 6 | 3 | 4 | | | | | | | | | |
| | A Hoang | 6 | 6 | | | | | | | 6 | L Pouille | 3 | 6$^3$ | | | | | |
| | G Soeda | 6$^4$ | 4 | | | | | | | 2 | A Rinderknech | 6 | 7$^7$ | | | | | |
| | T Lamasine | 7$^7$ | 6 | | | T Lamasine | 6$^8$ | 2 | | | | | | | | | | |
| | T Kamke | 3 | 6 | 3 | 2 | A Rinderknech | 7$^{10}$ | 6 | | | | | | | | | | |
| 2 | A Rinderknech | 6 | 3 | 6 | | | | | | | | | | | | | | |