2021 Stockholm Open

The 2021 Stockholm Open was a professional men's tennis tournament played on indoor hard courts. It was the 52nd edition of the tournament, and part of the ATP Tour 250 series of the 2021 ATP Tour. It took place at the Kungliga tennishallen in Stockholm, Sweden from 7 to 13 November 2021. Unseeded Tommy Paul won the singles title.

Singles
Paul won his first ATP Tour title.
 * 🇺🇸 Tommy Paul defeated 🇨🇦 Denis Shapovalov, 6–4, 2–6, 6–4

Doubles

 * 🇲🇽 Santiago González / 🇦🇷 Andrés Molteni defeated 🇵🇰 Aisam-ul-Haq Qureshi / Jean-Julien Rojer 6–2, 6–2.

Seeds

 * Rankings were as of November 1, 2021

Other entrants
The following players received wildcards into the singles main draw:
 * 🇸🇪 Leo Borg
 * 🇬🇧 Andy Murray
 * 🇸🇪 Elias Ymer

The following players received entry from the qualifying draw:
 * 🇳🇴 Viktor Durasovic
 * 🇺🇿 Denis Istomin
 * 🇷🇺 Pavel Kotov
 * 🇮🇹 Andrea Vavassori

The following players received entry as lucky losers:
 * 🇧🇾 Egor Gerasimov
 * 🇸🇰 Jozef Kovalík
 * Nino Serdarušić

Withdrawals

 * Before the tournament
 * Nikoloz Basilashvili → replaced by 🇺🇸 Tommy Paul
 * 🇦🇺 Alex de Minaur → replaced by 🇫🇷 Adrian Mannarino
 * 🇧🇬 Grigor Dimitrov → replaced by 🇫🇷 Arthur Rinderknech
 * Cristian Garín → replaced by 🇺🇸 Taylor Fritz
 * 🇫🇷 Ugo Humbert → replaced by 🇪🇸 Alejandro Davidovich Fokina
 * 🇵🇱 Hubert Hurkacz → replaced by 🇧🇾 Egor Gerasimov
 * 🇷🇺 Aslan Karatsev → replaced by Nino Serdarušić
 * 🇫🇷 Gaël Monfils → replaced by 🇭🇺 Márton Fucsovics
 * 🇬🇧 Cameron Norrie → replaced by 🇩🇪 Peter Gojowczyk
 * 🇳🇴 Casper Ruud → replaced by 🇺🇸 Mackenzie McDonald
 * 🇦🇷 Diego Schwartzman → replaced by 🇺🇸 Frances Tiafoe
 * 🇮🇹 Lorenzo Sonego → replaced by 🇸🇰 Jozef Kovalík
 * 🇩🇪 Alexander Zverev → replaced by 🇫🇮 Emil Ruusuvuori

Seeds

 * Rankings were as of November 1, 2021

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇸🇪 Markus Eriksson / 🇸🇪 Elias Ymer
 * 🇸🇪 André Göransson / 🇸🇪 Robert Lindstedt

The following pairs received entry into the doubles main draw as alternates:
 * 🇸🇪 Karl Friberg / 🇪🇬 Mohamed Safwat
 * 🇸🇪 Simon Freund / Nino Serdarušić

Withdrawals

 * Before the tournament
 * Marcelo Arévalo / 🇲🇽 Santiago González → replaced by 🇲🇽 Santiago González / 🇦🇷 Andrés Molteni
 * 🇮🇹 Simone Bolelli / 🇦🇷 Máximo González → replaced by 🇧🇦 Tomislav Brkić / 🇷🇸 Nikola Ćaćić
 * 🇮🇳 Rohan Bopanna / 🇨🇦 Denis Shapovalov → replaced by Ariel Behar / 🇪🇨 Gonzalo Escobar
 * 🇧🇪 Sander Gillé / 🇧🇪 Joran Vliegen → replaced by 🇫🇮 Emil Ruusuvuori / Botic van de Zandschulp
 * Wesley Koolhof / Jean-Julien Rojer → replaced by 🇵🇰 Aisam-ul-Haq Qureshi /  Jean-Julien Rojer
 * Raven Klaasen / 🇯🇵 Ben McLachlan → replaced by 🇫🇷 Fabrice Martin / Hugo Nys
 * 🇩🇪 Kevin Krawietz / 🇷🇴 Horia Tecău → replaced by 🇪🇸 Pedro Martínez / 🇮🇹 Andrea Vavassori
 * 🇬🇧 Jamie Murray / 🇧🇷 Bruno Soares → replaced by 🇺🇸 Taylor Fritz / 🇺🇸 Tommy Paul
 * 🇦🇺 John Peers / 🇸🇰 Filip Polášek → replaced by 🇸🇪 Karl Friberg / 🇪🇬 Mohamed Safwat
 * 🇩🇪 Tim Pütz / 🇳🇿 Michael Venus → replaced by 🇸🇪 Simon Freund / Nino Serdarušić