The 2021 Halle Open (known for sponsorship reasons as the 2021 Noventi Open) was a men's tennis tournament played on outdoor grass courts. It was the 28th edition of the Halle Open and part of the ATP Tour 500 series of the 2021 ATP Tour. It took place at the OWL Arena in Halle, Germany, between 14 June and 20 June 2021. Unseeded Ugo Humbert won the singles title.
<sub>*per team</sub>
The following players received wildcards into the main draw:
The following player received entry as a special exempt:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
The following pairs received wildcards into the doubles main draw:
The following pair received entry from the qualifying draw:
The following pair received entry as a lucky loser: