| Date: | 25–31 October |
| Edition: | 6th |
| Surface: | Hard (Indoor) |
| Location: | Brest, France |
| Champs: |  Brandon Nakashima |
| Champd: |  Sadio Doumbia / Fabien Reboul |
| Before Year: | 2019 |
The 2021 Brest Challenger was a professional tennis tournament played on hard courts. It was the sixth edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Brest, France between 25 and 31 October 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| France | Arthur Rinderknech | 65 | 1 | |
| France | Richard Gasquet | 74 | 3 | |
| Brandon Nakashima | 79 | 4 | ||
 Italy | Stefano Travaglia | 83 | 5 | |
| France | Pierre-Hugues Herbert | 97 | 6 | |
| Henri Laaksonen | 99 | 7 | ||
| France | Hugo Gaston | 106 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as a special exempt:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
Valentin RoyerSee main article: 2021 Brest Challenger – Singles.
Brandon Nakashima def. João Sousa 6–3, 6–3.See main article: 2021 Brest Challenger – Doubles.
Sadio Doumbia / Fabien Reboul def. Salvatore Caruso / Federico Gaio 4–6, 6–3, [10–3].
