| Singles | |
|---|---|
| 2021 Rio Tennis Classic | |
| Champion |  Kaichi Uchida |
| Runner-up |  Nicolás Álvarez Varona |
| Score | 3–6, 6–3, 7–6(7–3) |
Carlos Berlocq was the defending champion [1] but chose not to defend his title.
Kaichi Uchida won the title after defeating Nicolás Álvarez Varona 3–6, 6–3, 7–6(7–3) in the final.
Thiago Seyboth Wild (quarterfinals)
Nicolás Kicker (semifinals) Juan Pablo Ficovich (first round) Matheus Pucinelli de Almeida (withdrew)
Roberto Cid Subervi (first round, retired) Orlando Luz (first round)
Peđa Krstin (first round) Kaichi Uchida (champion)| Semifinals | Final | ||||||||||||
| 8 | Kaichi Uchida | 6 | 6 | ||||||||||
| WC | Gabriel Décamps | 2 | 3 | ||||||||||
| 8 | Kaichi Uchida | 3 | 6 | 77 | |||||||||
| Nicolás Álvarez Varona | 6 | 3 | 63 | ||||||||||
| Nicolás Álvarez Varona | 6 | 7 | |||||||||||
| 2 | Nicolás Kicker | 2 | 5 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | T Seyboth Wild | 6 | 6 | ||||||||||||||||||||||||
| WC | Lorenzo Esquici | 2 | 0 | 1 | T Seyboth Wild | 6 | 3 | 7 | |||||||||||||||||||
 J Nikles | 6 | 6 | J Nikles | 1 | 6 | 5 | |||||||||||||||||||||
| Q | L Castelnuovo | 2 | 4 | 1 | T Seyboth Wild | 4 | 1 | ||||||||||||||||||||
| GA Olivieri | 5 | 6 | 6 | 8 | K Uchida | 6 | 6 | ||||||||||||||||||||
| PR | G Clezar | 7 | 4 | 3 | GA Olivieri | 6 | 3 | 1 | |||||||||||||||||||
| G Villanueva | 3 | 4 | 8 | K Uchida | 3 | 6 | 6 | ||||||||||||||||||||
| 8 | K Uchida | 6 | 6 | 8 | K Uchida | 6 | 6 | ||||||||||||||||||||
| 3 | JP Ficovich | 6 | 1 | 2 | WC | G Décamps | 2 | 3 | |||||||||||||||||||
 A Gómez | 4 | 6 | 6 | A Gómez | 6 | 4 | 1 | ||||||||||||||||||||
| WC | G Décamps | 6 | 6 | WC | G Décamps | 3 | 6 | 6 | |||||||||||||||||||
| Q | N Barrientos | 1 | 4 | WC | G Décamps | 6 | 4 | 6 | |||||||||||||||||||
| Q | R Matos | 6 | 0 | 6 | D Dutra da Silva | 4 | 6 | 2 | |||||||||||||||||||
| WC | Wilson Leite | 4 | 6 | 2 | Q | R Matos | 3 | 0r | |||||||||||||||||||
| D Dutra da Silva | 78 | 6 | D Dutra da Silva | 6 | 0 | ||||||||||||||||||||||
| 6 | O Luz | 66 | 4 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 7 | P Krstin | 2 | 66 | ||||||||||||||||||||||||
 L Darderi | 6 | 78 | L Darderi | 3 | 1 | ||||||||||||||||||||||
| F Díaz Acosta | 3 | 6 | 3 | N Álvarez Varona | 6 | 6 | |||||||||||||||||||||
| N Álvarez Varona | 6 | 4 | 6 | N Álvarez Varona | 6 | 6 | |||||||||||||||||||||
| P Sakamoto | 6 | 4 | 6 | LL |  R Smith | 4 | 4 | ||||||||||||||||||||
| Facundo Juárez | 4 | 6 | 4 | P Sakamoto | 710 | 4 | 3 | ||||||||||||||||||||
| LL | Roy Smith | 6 | 77 | LL | R Smith | 68 | 6 | 6 | |||||||||||||||||||
| LL |  F Zeballos | 4 | 64 | N Álvarez Varona | 6 | 7 | |||||||||||||||||||||
| 5 | R Cid Subervi | 3 | 0r | 2 | N Kicker | 2 | 5 | ||||||||||||||||||||
 B Bobrov | 6 | 1 | B Bobrov | 64 | 6 | 3 | |||||||||||||||||||||
| MF Descotte | 63 | 4 | Alt | M Alves | 77 | 3 | 6 | ||||||||||||||||||||
| Alt | M Alves | 77 | 6 | Alt | M Alves | 6 | 64 | 4 | |||||||||||||||||||
| Q | J Pereira | 2 | 7 | 4 | 2 | N Kicker | 3 | 77 | 6 | ||||||||||||||||||
| SE | I Marcondes | 6 | 5 | 6 | SE | I Marcondes | 4 | 1 | |||||||||||||||||||
| A González | 5 | 3 | 2 | N Kicker | 6 | 6 | |||||||||||||||||||||
| 2 | N Kicker | 7 | 6 | ||||||||||||||||||||||||
Filip Horanský and Jiří Veselý were the defending champions but were both ineligible to compete.
Bjorn Fratangelo was the defending champion, but was not eligible to participate.
Kimmer Coppejans won this event, defeating 5th-seed Filip Peliwo 6–1, 6–4 in the final.
Andrés Artuñedo and Roberto Carballés were the defending champions.
Andrew Harris and Nick Kyrgios won the title by defeating Adam Pavlásek and Václav Šafránek in the final, 6–4, 2–6, [10–7]
Filip Peliwo defeated the defending champion Luke Saville in the final, 7–5, 6–4 to win the boys' singles tennis title at the 2012 Wimbledon Championships.
Pablo Cuevas was the two-time defending champion and successfully defended his title, defeating Albert Ramos Viñolas in the final, 6–7(3–7), 6–4, 6–4.
Scott Griekspoor was the defending champion but lost in the second round to Tristan Lamasine.
Jason Kubler was the defending champion but chose not to defend his title.
Luca Nardi was the defending champion but lost in the second round to Jack Draper.
Marco Bortolotti and Arjun Kadhe were the defending champions but lost in the first round to Kaichi Uchida and Wu Tung-lin.
Andrej Martin was the defending champion but chose not to defend his title.
Nikola Ćaćić and Yang Tsung-hua were the defending champions but chose not to defend their title.
Emilio Nava was the defending champion but lost in the semifinals to Sergey Fomin.
Christian Harrison and Peter Polansky were the defending champions but only Harrison chose to defend his title, partnering Andrew Harris. Harrison lost in the semifinals to Chung Yun-seong and Michail Pervolarakis.
Gastão Elias was the three-time defending champion but chose not to defend his title.
Norbert Gombos was the defending champion but chose not to defend his title.
Daniil Medvedev defeated the defending champion Cameron Norrie in the final, 7–5, 6–0 to win the singles tennis title. It was his 14th career ATP Tour title, his first of the season, and his first since the 2021 US Open eleven months earlier.
Lukáš Lacko was the defending champion but retired in the final round of qualifying in his match against Daniil Glinka.
Kwon Soon-woo was the defending champion but chose not to defend his title.
Yosuke Watanuki was the defending champion and successfully defended his title, defeating Frederico Ferreira Silva 6–7(3–7), 7–5, 6–4 in the final.
Kaichi Uchida was the defending champion but lost in the quarterfinals to Juan Manuel Cerúndolo.