The 2021 Slovak Open II was a professional tennis tournament played on hard courts.

It was the 23rd edition of the tournament which was part of the 2021 ATP Challenger Tour.

It took place in Bratislava, Slovakia between 8 and 14 November 2021.

The following players received wildcards into the singles main draw: The following player received entry into the singles main draw as an alternate: The following players received entry from the qualifying draw: The following players received entry as lucky losers: