The 2021 Sparkassen Open was a professional tennis tournament played on clay courts. It was the 27th edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Braunschweig, Germany between 5 and 11 July 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 France | Benoît Paire | 46 | 1 | |
 Lithuania | ||||
| Yannick Hanfmann | 99 | 3 | ||
 Slovakia | Jozef Kovalík | 127 | 4 | |
| Henri Laaksonen | 137 | 5 | ||
 Czech Republic | Tomáš Macháč | 144 | 6 | |
 India | Sumit Nagal | 150 | 7 | |
| Daniel Altmaier | 166 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry into the singles main draw as alternates:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
See main article: 2021 Sparkassen Open – Singles.
See main article: 2021 Sparkassen Open – Doubles.
Szymon Walków / Jan Zieliński def. Ivan Sabanov / Matej Sabanov 6–4, 4–6, [10–4].
