The 2021 Maia Challenger was a professional tennis tournament played on clay courts. It was the third edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Maia, Portugal from 6 to 12 December 2021.
The following players received wildcards into the singles main draw:
The following players received entry into the singles main draw using protected rankings:
The following players received entry from the qualifying draw:
