2021 European Open

The 2021 European Open was a men's tennis tournament played on indoor hard courts. It was the sixth edition of the European Open and part of the ATP Tour 250 series of the 2021 ATP Tour. It took place at the Lotto Arena in Antwerp, Belgium, from 18 October until 24 October 2021.

Singles

 * 🇮🇹 Jannik Sinner defeated 🇦🇷 Diego Schwartzman, 6–2, 6–2

Doubles

 * 🇫🇷 Nicolas Mahut / 🇫🇷 Fabrice Martin defeated Wesley Koolhof /  Jean-Julien Rojer, 6–0, 6–1

Seeds

 * Rankings are as of 4 October 2021.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇧🇪 Zizou Bergs
 * 🇫🇷 Richard Gasquet
 * 🇬🇧 Andy Murray

The following players received entry from the qualifying draw:
 * 🇺🇸 Jenson Brooksby
 * Henri Laaksonen
 * 🇺🇸 Brandon Nakashima
 * 🇦🇹 Dennis Novak

Withdrawals

 * Before the tournament
 * 🇨🇦 Félix Auger-Aliassime → replaced by 🇦🇺 Alexei Popyrin
 * Nikoloz Basilashvili → replaced by 🇮🇹 Gianluca Mager
 * 🇪🇸 Pablo Carreño Busta → replaced by 🇦🇺 Jordan Thompson
 * 🇧🇬 Grigor Dimitrov → replaced by 🇫🇷 Arthur Rinderknech
 * 🇮🇹 Fabio Fognini → replaced by 🇮🇹 Lorenzo Musetti
 * 🇫🇷 Ugo Humbert → replaced by 🇩🇪 Jan-Lennard Struff
 * 🇬🇧 Cameron Norrie → replaced by Botic van de Zandschulp

Seeds

 * Rankings are as of 4 October 2021.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇧🇪 Ruben Bemelmans / 🇧🇪 Kimmer Coppejans
 * Lloyd Harris / 🇧🇪 Xavier Malisse

Withdrawals

 * Before the tournament
 * 🇮🇹 Simone Bolelli / 🇦🇷 Máximo González → replaced by David Pel /  Botic van de Zandschulp
 * 🇧🇬 Grigor Dimitrov / Frederik Nielsen → replaced by  Frederik Nielsen /  Matej Sabanov
 * 🇮🇹 Fabio Fognini / 🇨🇿 Roman Jebavý → replaced by 🇨🇿 Roman Jebavý / 🇧🇾 Andrei Vasilevski
 * Cristian Garín / 🇪🇸 David Vega Hernández → replaced by 🇦🇷 Federico Delbonis / 🇪🇸 David Vega Hernández
 * Nikola Mektić / Mate Pavić → replaced by 🇮🇱 Jonathan Erlich / 🇸🇪 André Göransson
 * 🇦🇺 John Peers / 🇸🇰 Filip Polášek → replaced by Romain Arneodo / 🇦🇺 Matt Reid
 * 🇩🇪 Tim Pütz / 🇳🇿 Michael Venus → replaced by 🇺🇦 Denys Molchanov / 🇰🇿 Aleksandr Nedovyesov


 * During the tournament
 * 🇮🇹 Lorenzo Musetti / 🇫🇷 Benoît Paire