| Doubles | |
|---|---|
| 2021 Belgrade Open | |
| Champions |  Jonathan Erlich  Andrei Vasilevski |
| Runners-up |  André Göransson  Rafael Matos |
| Final score | 6–4, 6–1 |
This was the first edition of the tournament, primarily created due to the one-week delay of the 2021 French Open. [1]
Jonathan Erlich and Andrei Vasilevski won the title, defeating André Göransson and Rafael Matos in the final, 6–4, 6–1.
Rohan Bopanna / 
Franko Škugor (first round)
Fabrice Martin / 
Hugo Nys (first round)
Ariel Behar / 
Gonzalo Escobar (first round) Marcelo Demoliner / 
Santiago González (quarterfinals)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | R Bopanna F Škugor | 3 | 6 | [8] | |||||||||||||||||||||||
 F Delbonis  A Sitak | 6 | 4 | [10] | F Delbonis A Sitak | 2 | 1 | |||||||||||||||||||||
| WC | I Sabanov M Sabanov | 4 | 6 | [10] | WC | I Sabanov M Sabanov | 6 | 6 | |||||||||||||||||||
 T Brkić  N Ćaćić | 6 | 3 | [8] | WC | I Sabanov M Sabanov | 3 | 6 | [11] | |||||||||||||||||||
| 3 | A Behar G Escobar | 7 | 63 | [4] | J Erlich A Vasilevski | 6 | 3 | [13] | |||||||||||||||||||
 S Arends  LD Martínez | 5 | 77 | [10] | S Arends LD Martínez | 3 | 6 | [6] | ||||||||||||||||||||
| J Erlich A Vasilevski | 6 | 4 | [10] | J Erlich A Vasilevski | 6 | 0 | [10] | ||||||||||||||||||||
A Molteni  F Nielsen | 4 | 6 | [3] | J Erlich A Vasilevski | 6 | 6 | |||||||||||||||||||||
 R Carballés Baena F Coria | 3 | 4 | A Göransson R Matos | 4 | 1 | ||||||||||||||||||||||
 L Bambridge D Inglot | 6 | 6 | L Bambridge D Inglot | 6 | 6 | ||||||||||||||||||||||
| WC | H Međedović M Tepavac | 60 | 6 | [9] | 4 | M Demoliner S González | 4 | 4 | |||||||||||||||||||
| 4 | M Demoliner S González | 77 | 3 | [11] | L Bambridge D Inglot | 63 | 6 | [4] | |||||||||||||||||||
| A Göransson R Matos | 6 | 5 | [10] | A Göransson R Matos | 77 | 1 | [10] | ||||||||||||||||||||
D Sharan  J-P Smith | 4 | 7 | [6] | A Göransson R Matos | 6 | 6 | |||||||||||||||||||||
 A Krajicek T Sandgren | 6 | 65 | [10] | A Krajicek T Sandgren | 1 | 3 | |||||||||||||||||||||
| 2 | F Martin H Nys | 3 | 77 | [8] | |||||||||||||||||||||||
Svetlana Kuznetsova was the defending champion, but chose not to play that year.
Yuki Bhambri was the defending champion, but did not compete in the Juniors this year.
Venus Williams was the two-time defending champion, but withdrew before the tournament started due to injury.
Pieter Aldrich and Danie Visser were the defending champions, but lost in the first round to Paul Haarhuis and Mark Koevermans.
Scott Davis and David Pate won the title, defeating Patrick McEnroe and David Wheaton 6–1, 4–6, 6–4, 5–7, 9–7, in the final. This was Pate's first Grand Slam title and final, despite gaining the World No. 1 ranking two weeks earlier.
John Fitzgerald and Anders Järryd lost in the third round to McEnroe and Wheaton. It was their only Grand Slam loss of the year, as they would go on to win the following three majors in 1991.
Monica Seles was the reigning champion but did not compete this year, as she decided to play in Dubai in the same week.
The United States Open Tennis Championships is a hardcourt tennis tournament held annually at Flushing Meadows, starting on the last Monday in August and lasting for two weeks. The tournament consists of five main championship events: men's and women's singles, men's and women's doubles, and mixed doubles, with additional tournaments for seniors, juniors, and wheelchair players.
Julie Halard-Decugis was the defending champion, but decided to compete in Gold Coast at the same week.
Akiko Morigami and Saori Obata were the defending champions, but Obata decided to compete in Hyderabad that week. Morigami teamed up with Alina Jidkova and lost in the first round to Gisela Dulko and Patricia Tarabini.
Virginia Ruano Pascual was the defending champion, but decided to compete in Moscow at the same week.
Jelena Janković was the defending champion, but decided to compete in Stanford at the same week.
Marcel Granollers and Rajeev Ram were the defending champions, but chose to compete with different partners. Granollers played alongside Horacio Zeballos, but lost in the second round to Jamie Murray and Neal Skupski. Ram teamed up with Joe Salisbury, but lost in the quarterfinals to Ivan Dodig and Filip Polášek.
Thomas Muster was the defending champion, but chose to compete in Stuttgart at the same week.
Andre Agassi was the defending champion, but was defeated in the final to Pete Sampras with a score of 7–6(7–3), 7–6(7–1). By reaching the final, Sampras completed his 271st week at the world No. 1 ranking in his career, surpassing the previous record of 270 weeks established by Ivan Lendl.
Cristian Garín was the defending champion, but chose not to defend his title.
This was the first edition of the tournament, primarily created due to the one-week delay of the 2021 French Open.
Miomir Kecmanović was the defending champion, but chose to compete at the Summer Olympics instead.
Jeļena Ostapenko was the defending champion, having won the previous edition in 2019, but lost to Clara Tauson in the final, 3–6, 6–4, 4–6.
Donald Johnson and Francisco Montana were the defending champions, but Johnson chose to compete at Basel in the same week. Montana teamed up with Nebojša Đorđević and lost in the first round to Pablo Albano and Guillermo Cañas.
Albert Costa was the defending champions, but chose to compete at Cincinnati in the same week.
Pablo Albano and Lucas Arnold Ker were the defending champions, but Albano chose to compete at Cincinnati at the same week. Arnold Ker teamed up with Tom Vanhoudt and lost in the first round to Wayne Arthurs and Richard Fromberg.
| Grand Slam events | |
|---|---|
| ATP Tour Masters 1000 | |
| ATP Tour 500 | |
| ATP Tour 250 |
|
| Team events | |
 – Tournaments are affected by the COVID-19 pandemic * – Tournaments are introduced due to the impact of the COVID-19 pandemic | |