See main article: Vienna Open.
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.[1]
See main article: 2021 Erste Bank Open – Singles.
Frances Tiafoe, 7–5, 6–4See main article: 2021 Erste Bank Open – Doubles.
Juan Sebastián Cabal / Robert Farah def. Rajeev Ram / 
Joe Salisbury, 6–4, 6–2| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Stefanos Tsitsipas | 3 | 1 | ||
| Alexander Zverev | 4 | 2 | ||
| Matteo Berrettini | 7 | 3 | ||
| Casper Ruud | 9 | 4 | ||
 Poland | Hubert Hurkacz | 10 | 5 | |
| Félix Auger-Aliassime | 12 | 6 | ||
 Italy | Jannik Sinner | 13 | 7 | |
 Argentina | Diego Schwartzman | 14 | 8 |
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:
Ugo Humbert → replaced by 
Márton Fucsovics| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
| Nikola Mektić | Mate Pavić | 3 | 1 | |||
| Rajeev Ram | United Kingdom | Joe Salisbury | 7 | 2 | ||
 Australia | John Peers |  Slovakia | Filip Polášek | 22 | 3 | |
| Colombia | Juan Sebastián Cabal | Colombia | Robert Farah | 27 | 4 |
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:
Cameron Norrie → replaced by 
Sander Gillé / Dominik Koepfer
Horia Tecău → replaced by Lloyd Harris / Horia Tecău
