| Men's singles | |
|---|---|
| 2021 Belgrade Challenger | |
| Champion |  Roberto Carballés Baena |
| Runner-up |  Damir Džumhur |
| Final score | 6–4, 7–5 |
This was the first of the three tournaments held in Belgrade for the 2021 tennis season. Belgrade also hosted a joint ATP/WTA tournament. [1]
Roberto Carballés Baena won the title after defeating Damir Džumhur 6–4, 7–5 in the final.
Roberto Carballés Baena (champion)
Facundo Bagnis (quarterfinals)
Daniel Elahi Galán (first round)
Philipp Kohlschreiber (second round) Francisco Cerúndolo (first round)
Taro Daniel (quarterfinals)
Hugo Dellien (second round)
Benjamin Bonzi (second round)| Semifinals | Final | ||||||||||||
| 1 | Roberto Carballés Baena | 3 | 6 | 6 | |||||||||
 Liam Broady | 6 | 2 | 3 | ||||||||||
| 1 | Roberto Carballés Baena | 6 | 7 | ||||||||||
| Damir Džumhur | 4 | 5 | |||||||||||
| Damir Džumhur | 3 | 6 | 6 | ||||||||||
 Jozef Kovalík | 6 | 3 | 3 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | R Carballés Baena | 6 | 77 | ||||||||||||||||||||||||
| A Rinderknech | 4 | 64 | 1 | R Carballés Baena | 6 | 6 | |||||||||||||||||||||
| Q | M Trungelliti | 6 | 6 | Q | M Trungelliti | 2 | 4 | ||||||||||||||||||||
 D Petrović | 3 | 2 | 1 | R Carballés Baena | 79 | 6 | |||||||||||||||||||||
| SE |  B Rola | 6 | 2 | SE | B Rola | 67 | 1 | ||||||||||||||||||||
| Q |  A Giannessi | 4 | 0r | SE | B Rola | 6 | 6 | ||||||||||||||||||||
| SE |  G Oliveira | 0r | 8 | B Bonzi | 2 | 2 | |||||||||||||||||||||
| 8 | B Bonzi | 4 | 1 | R Carballés Baena | 3 | 6 | 6 | ||||||||||||||||||||
| 3 | DE Galán | 5 | 6 | 4 | L Broady | 6 | 2 | 3 | |||||||||||||||||||
 S Ofner | 7 | 3 | 6 | S Ofner | 6 | 1 | 5 | ||||||||||||||||||||
| L Broady | 6 | 6 | L Broady | 4 | 6 | 7 | |||||||||||||||||||||
| N Milojević | 3 | 4 | L Broady | 6 | 62 | 6 | |||||||||||||||||||||
 B Nakashima | 67 | 6 | 6 | B Nakashima | 4 | 77 | 4 | ||||||||||||||||||||
| Q |  E Benchetrit | 79 | 1 | 0 | B Nakashima | 6 | 6 | ||||||||||||||||||||
 T Griekspoor | 67 | 4 | 7 | H Dellien | 2 | 2 | |||||||||||||||||||||
| 7 | H Dellien | 79 | 6 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 6 | T Daniel | 6 | 7 | ||||||||||||||||||||||||
| WC | M Miladinović | 1 | 5 | 6 | T Daniel | 6 | 6 | ||||||||||||||||||||
| Q | M Bachinger | 7 | 4 | 0r | A Hoang | 4 | 2 | ||||||||||||||||||||
| A Hoang | 5 | 6 | 0 | 6 | T Daniel | 4 | 4 | ||||||||||||||||||||
| D Džumhur | 4 | 6 | 6 | D Džumhur | 6 | 6 | |||||||||||||||||||||
| WC | P Krstin | 6 | 2 | 3 | D Džumhur | 6 | 6 | ||||||||||||||||||||
| M Cressy | 5 | 6 | 2 | 4 | P Kohlschreiber | 4 | 3 | ||||||||||||||||||||
| 4 | P Kohlschreiber | 7 | 4 | 6 | D Džumhur | 3 | 6 | 6 | |||||||||||||||||||
| 5 | F Cerúndolo | 66 | 1 | J Kovalík | 6 | 3 | 3 | ||||||||||||||||||||
| J Kovalík | 78 | 6 | J Kovalík | 6 | 77 | ||||||||||||||||||||||
 E Donskoy | 4 | 3 | F Gaio | 0 | 64 | ||||||||||||||||||||||
| F Gaio | 6 | 6 | J Kovalík | 2 | 6 | 6 | |||||||||||||||||||||
| O Otte | 3 | 6 | 3 | 2 | F Bagnis | 6 | 4 | 4 | |||||||||||||||||||
| WC | H Međedović | 6 | 1 | 6 | WC | H Međedović | 2 | 2 | |||||||||||||||||||
| J Rodionov | 6 | 1 | 2 | 2 | F Bagnis | 6 | 6 | ||||||||||||||||||||
| 2 | F Bagnis | 2 | 6 | 6 | |||||||||||||||||||||||
Stanislas Wawrinka was the defending champion, but withdrew before the event started.
Carlos Berlocq won the title, defeating Tomáš Berdych in the final, 0–6, 7–5, 6–1.
Dominic Thiem was the defending champion, having won the previous tournament in 2013, but concentrating on the ATP tour he did not participate this year.
Richard Gasquet won the title, defeating Nick Kyrgios in the final, 6–3, 6–2.
This was the first edition of the tournament since 2011.
This was the first edition of the tournament, Damir Džumhur won the title defeating Daniel Muñoz de la Nava in the final
This was the first edition of the tournament.
Roberto Carballés Baena was the defending champion but retired in the second round facing Maximilian Marterer.
Roberto Carballés Baena was the defending champion but lost in the quarterfinals to Uladzimir Ignatik.
This was the first edition of the tournament.
Víctor Estrella Burgos was the three-time defending champion and the tournament's only champion to date, but lost in the second round to Gerald Melzer.
Dominic Thiem was the defending champion, but lost in the quarterfinals to Fernando Verdasco.
This was the first edition of the tournament.
This was the first edition of the tournament.
Matteo Berrettini was the defending champion, but withdrew with an ankle injury before the tournament began.
Juan Pablo Varillas was the defending champion but chose not to participate.
Matteo Berrettini defeated Aslan Karatsev in the final, 6–1, 3–6, 7–6(7–0), to win the men's singles tennis title at the 2021 Serbia Open.
Albert Ramos Viñolas defeated Cameron Norrie in the final, 4–6, 6–3, 7–6(7–3) to win the singles tennis title at the 2021 Estoril Open. It marked his third career ATP Tour singles title, all of which have been on clay. Norrie was aiming to win his first ATP Tour title in his second final.
This was the first edition of the tournament, primarily created due to the one-week delay of the 2021 French Open.
This was the first edition of the tournament.
Carlos Alcaraz defeated Diego Schwartzman in the final, 6–4, 6–2 to win the singles title at the 2022 Rio Open. Alcaraz became the youngest winner of an ATP Tour 500 event since the category was created in 2009.