2021 Erste Bank 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.

Singles

 * 🇩🇪 Alexander Zverev def. 🇺🇸 Frances Tiafoe, 7–5, 6–4

Doubles

 * 🇨🇴 Juan Sebastián Cabal / 🇨🇴 Robert Farah def. 🇺🇸 Rajeev Ram / 🇬🇧 Joe Salisbury, 6–4, 6–2

Seeds

 * Rankings are as of October 18, 2021

Other entrants
The following players received wildcards into the singles main draw:
 * 🇬🇧 Andy Murray
 * 🇮🇹 Lorenzo Musetti
 * 🇦🇹 Dennis Novak

The following player received entry using a special exempt:
 * 🇱🇹 Ričardas Berankis

The following players received entry from the qualifying draw:
 * Kevin Anderson
 * 🇮🇹 Gianluca Mager
 * 🇦🇺 Alexei Popyrin
 * 🇺🇸 Frances Tiafoe

The following player received entry as a lucky loser:
 * 🇩🇪 Dominik Koepfer

Withdrawals

 * Before the tournament
 * Cristian Garín → replaced by 🇩🇪 Dominik Koepfer
 * 🇫🇷 Ugo Humbert → replaced by 🇭🇺 Márton Fucsovics

Seeds

 * Rankings are as of 18 October 2021

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇪🇸 Feliciano López / Stefanos Tsitsipas
 * 🇦🇹 Oliver Marach / 🇦🇹 Philipp Oswald

The following pair received entry from the qualifying draw:
 * 🇦🇹 Alexander Erler / 🇦🇹 Lucas Miedler

The following pair received entry as lucky losers:
 * 🇧🇪 Sander Gillé / 🇩🇪 Dominik Koepfer

Withdrawals

 * Before the tournament
 * Cristian Garín / 🇬🇧 Cameron Norrie → replaced by 🇧🇪 Sander Gillé / 🇩🇪 Dominik Koepfer
 * 🇩🇪 Kevin Krawietz / 🇷🇴 Horia Tecău → replaced by Lloyd Harris / 🇷🇴 Horia Tecău