| Singles | |
|---|---|
| 2021 Open de Oeiras II | |
| Champion |  Pedro Cachin |
| Runner-up |  Nuno Borges |
| Score | 7–6(7–4), 7–6(7–3) |
This was the second of four editions of the tournament in the 2021 ATP Challenger Tour calendar. [1]
Zdeněk Kolář was the defending champion but chose not to defend his title.
Pedro Cachin won the title after defeating Nuno Borges 7–6(7–4), 7–6(7–3) in the final.
Oscar Otte (second round)
Enzo Couacaud (first round)
Ernesto Escobedo (second round)
Elliot Benchetrit (first round)
Gian Marco Moroni (quarterfinals) Marco Trungelliti (first round)
Nicola Kuhn (first round) Tristan Lamasine (first round)| Semifinals | Final | ||||||||||||
| Gonçalo Oliveira | 64 | 0r | |||||||||||
| Q | Pedro Cachin | 77 | 4 | ||||||||||
| Q | Pedro Cachin | 77 | 77 | ||||||||||
| WC | Nuno Borges | 64 | 63 | ||||||||||
| SE | Gastão Elias | 6 | 2 | 3 | |||||||||
| WC | Nuno Borges | 4 | 6 | 6 | |||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | O Otte | 6 | 6 | ||||||||||||||||||||||||
| WC | Pedro Araújo | 2 | 4 | 1 | O Otte | 4 | 6 | 3 | |||||||||||||||||||
| R Bonadio | 64 | 5 | G Oliveira | 6 | 4 | 6 | |||||||||||||||||||||
| G Oliveira | 77 | 7 | G Oliveira | 7 | 6 | ||||||||||||||||||||||
| M Zverev | 4 | WC | T Cação | 5 | 2 | ||||||||||||||||||||||
| M Moraing | 3r | M Zverev | 3 | 6 | 66 | ||||||||||||||||||||||
| WC | T Cação | 6 | 6 | WC | T Cação | 6 | 1 | 78 | |||||||||||||||||||
| 8 | T Lamasine | 2 | 4 | G Oliveira | 64 | 0r | |||||||||||||||||||||
| 4 | E Benchetrit | 2 | 1 | Q | P Cachin | 77 | 4 | ||||||||||||||||||||
| Q | P Cachin | 6 | 6 | Q | P Cachin | 6 | 6 | ||||||||||||||||||||
 C-h Tseng | 6 | 65 | 3 | Q |  A Andreev | 2 | 4 | ||||||||||||||||||||
| Q | A Andreev | 1 | 77 | 6 | Q | P Cachin | 6 | 2 | 6 | ||||||||||||||||||
 P Kotov | 6 | 3 | 5 | GM Moroni | 3 | 6 | 4 | ||||||||||||||||||||
| Alt |  H Bourchier | 0 | 0r | P Kotov | 2 | 2 | |||||||||||||||||||||
 A Molčan | 2 | 4 | 5 | GM Moroni | 6 | 6 | |||||||||||||||||||||
| 5 | GM Moroni | 6 | 6 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 6 | M Trungelliti | 1 | 4 | ||||||||||||||||||||||||
| SE | G Elias | 6 | 6 | SE | G Elias | 6 | 6 | ||||||||||||||||||||
| C Gimeno Valero | 6 | 6 | C Gimeno Valero | 1 | 3 | ||||||||||||||||||||||
| R Ortega Olmedo | 1 | 1 | SE | G Elias | w/o | ||||||||||||||||||||||
| D Kuzmanov | 6 | 6 | D Kuzmanov | ||||||||||||||||||||||||
 L Miedler | 1 | 0 | D Kuzmanov | 6 | 6 | ||||||||||||||||||||||
| Q | E Furness | 3 | 2 | 3 | E Escobedo | 2 | 2 | ||||||||||||||||||||
| 3 | E Escobedo | 6 | 6 | SE | G Elias | 6 | 2 | 3 | |||||||||||||||||||
| 7 | N Kuhn | 1 | 4 | WC | N Borges | 4 | 6 | 6 | |||||||||||||||||||
| M Guinard | 6 | 6 | M Guinard | 6 | 6 | ||||||||||||||||||||||
| H Grenier | 6 | 6 | H Grenier | 4 | 1 | ||||||||||||||||||||||
 D-h Lee | 0 | 3 | M Guinard | 3 | 6 | 3 | |||||||||||||||||||||
| Alt |  J Forejtek | 3r | WC | N Borges | 6 | 3 | 6 | ||||||||||||||||||||
| Q | R Brancaccio | 4 | Q | R Brancaccio | 4 | 6 | 3 | ||||||||||||||||||||
| WC | N Borges | 6 | 6 | WC | N Borges | 6 | 4 | 6 | |||||||||||||||||||
| 2 | E Couacaud | 3 | 4 | ||||||||||||||||||||||||
Roger Federer was the defending champion, but withdrew due to fatigue.
Radek Štěpánek was the defending champion, but opted to play at the London Summer Olympics instead.
Alexandr Dolgopolov defeated Tommy Haas in three sets for the title, 6–7(7–9), 6–4, 6–1.
Víctor Estrella Burgos was the two-time defending champion and successfully defended his title, defeating Paolo Lorenzi in the final, 6–7(2–7), 7–5, 7–6(8–6).
Lucas Pouille was the defending champion, but lost in the second round to John Millman.
Andrey Rublev was the defending champion, but lost in the quarterfinals to Robin Haase. This was Rublev's first tournament back on tour after missing three months due to a stress fracture in his back.
Leonardo Mayer was the defending champion, but lost in the final to Nikoloz Basilashvili, 4–6, 6–0, 5–7. This was Basilashvili's first ATP World Tour title, as well as the first ATP title won by a Georgian player since Alexander Metreveli.
Cristian Garín defeated Casper Ruud in the final, 7–6(7–4), 4–6, 6–3, to win the singles tennis title at the 2019 U.S. Men's Clay Court Championships. The win earned Garín his first career Association of Tennis Professionals (ATP) singles title and made him the first Chilean ATP title holder in ten years. Ruud was also in contention to win his first ATP Tour title after reaching his first final, joining father Christian Ruud as the only two Norwegian players to reach a final at this level.
Michael Mmoh was the defending champion but lost in the second round to Brandon Nakashima.
Kyle Edmund was the defending champion but chose not to defend his title.
Andrey Rublev defeated Márton Fucsovics in the final, 7–6(7–4), 6–4 to capture the men's singles tennis title at the 2021 Rotterdam Open. It was Rublev's fourth consecutive ATP Tour 500 victory, dating back to the 2020 Hamburg Open.
This was the first of four editions of the tournament in the 2021 ATP Challenger Tour calendar.
Alexander Zverev was the defending champion from when the event was held in 2019, but chose not to defend his title.
Ugo Humbert defeated Andrey Rublev in the final 6–3, 7–6(7–4), to win the singles tennis title at the 2021 Halle Open. Humbert's win earned him his third career ATP Tour singles title and his first ATP 500 victory, and also made him the first French player to win the tournament since Henri Leconte won the inaugural edition in 1993. Both Humbert and Rublev were contesting their first career final on grass.
Adrian Ungur was the defending champion when the event was last held in 2014 but chose not to defend his title as he had retired from professional tennis.
Novak Djokovic defeated the defending champion Daniil Medvedev in the final, 4–6, 6–3, 6–3 to win the singles tennis title at the 2021 Paris Masters. It was his record-extending sixth Paris Masters title and record-breaking 37th ATP Tour Masters 1000 title overall, surpassing Rafael Nadal's tally in the latter category.
Casper Ruud defeated the defending champion Diego Schwartzman in the final, 5–7, 6–2, 6–3 to win the singles title at the 2022 Argentina Open.
Novak Djokovic defeated Stefanos Tsitsipas in the final, 6–0, 7–6(7–5) to win the men's singles tennis title at the 2022 Italian Open. It was his sixth Italian Open title and record-extending 38th Masters 1000 title overall. Djokovic did not lose a set during the tournament, and won his 1000th ATP Tour-level career match against Casper Ruud in the semifinals.
Defending champion Casper Ruud defeated João Sousa in the final, 7–6(7–3), 4–6, 7–6(7–1) to win the singles tennis title at the 2022 Geneva Open.
Jannik Sinner defeated the defending champion Carlos Alcaraz in the final, 6–7(5–7), 6–1, 6–1 to win the singles tennis title at the 2022 Croatia Open Umag.
Nuno Borges and Francisco Cabral were the defending champions but chose not to defend their title.