The 2021 Erste Bank Open was a men's tennis tournament played on indoor hard courts. It was the 47th edition of the event, and part of the ATP Tour 500 Series of the 2021 ATP Tour. It was held at the Wiener Stadthalle in Vienna, Austria, from 25 until 31 October 2021. Second-seeded Alexander Zverev won the singles title.
The following players received wildcards into the singles main draw:
The following player received entry using 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 lucky losers: