| Singles | |
|---|---|
| 2021 Zagreb Open | |
| Champion |  Sebastián Báez |
| Runner-up |  Juan Pablo Varillas |
| Final score | 3–6, 6–3, 6–1 |
This was the first edition of the tournament since 2011. [1]
Sebastián Báez won the title after defeating Juan Pablo Varillas 3–6, 6–3, 6–1 in the final.
Federico Coria (second round)
Pedro Martínez (quarterfinals)
Andrej Martin (second round)
Yasutaka Uchiyama (first round)
Pedro Sousa (first round)
Benjamin Bonzi (first round)
Damir Džumhur (second round)
Thiago Seyboth Wild (quarterfinals)| Semifinals | Final | ||||||||||||
| Juan Manuel Cerúndolo | 1r | ||||||||||||
| Juan Pablo Varillas | 5 | ||||||||||||
| Juan Pablo Varillas | 6 | 3 | 1 | ||||||||||
| Q | Sebastián Báez | 3 | 6 | 6 | |||||||||
| Q |  Marcelo Tomás Barrios Vera | 3 | 4 | ||||||||||
| Q | Sebastián Báez | 6 | 6 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | F Coria | 6 | 79 | ||||||||||||||||||||||||
 M Safwat | 4 | 67 | 1 | F Coria | 64 | 2 | |||||||||||||||||||||
| JM Cerúndolo | 6 | 6 | JM Cerúndolo | 77 | 6 | ||||||||||||||||||||||
 E Donskoy | 3 | 2 | JM Cerúndolo | 6 | 63 | 6 | |||||||||||||||||||||
 B van de Zandschulp | 6 | 3 | 7 | B van de Zandschulp | 4 | 77 | 2 | ||||||||||||||||||||
 M Mmoh | 4 | 6 | 5 | B van de Zandschulp | 6 | 2 | 6 | ||||||||||||||||||||
| A Tabilo | 6 | 6 | A Tabilo | 1 | 6 | 4 | |||||||||||||||||||||
| 6 | B Bonzi | 4 | 1 | JM Cerúndolo | 1r | ||||||||||||||||||||||
| 4 | Y Uchiyama | 3 | 2 | JP Varillas | 5 | ||||||||||||||||||||||
 N Milojević | 6 | 6 | N Milojević | 77 | 6 | ||||||||||||||||||||||
| L Mayer | 6 | 64 | 6 | L Mayer | 64 | 2 | |||||||||||||||||||||
| F Ferreira Silva | 3 | 77 | 3 | N Milojević | 63 | 3 | |||||||||||||||||||||
| WC |  Antun Vidak | 0 | 1 | JP Varillas | 77 | 6 | |||||||||||||||||||||
 B Rola | 6 | 6 | B Rola | 4 | 2 | ||||||||||||||||||||||
| JP Varillas | 77 | 7 | JP Varillas | 6 | 6 | ||||||||||||||||||||||
| 5 | P Sousa | 64 | 5 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 8 | T Seyboth Wild | 0 | 7 | 7 | |||||||||||||||||||||||
| R Safiullin | 6 | 5 | 5 | 8 | T Seyboth Wild | 7 | 6 | ||||||||||||||||||||
| Q |  E Gulbis | 65 | 65 | WC | B Gojo | 5 | 4 | ||||||||||||||||||||
| WC | B Gojo | 77 | 77 | 8 | T Seyboth Wild | 4 | 2 | ||||||||||||||||||||
| Alt |  D Popko | 4 | 2 | Q | MT Barrios Vera | 6 | 6 | ||||||||||||||||||||
| Q | MT Barrios Vera | 6 | 6 | Q | MT Barrios Vera | 2 | 6 | 6 | |||||||||||||||||||
 J Jung | 6 | 64 | 0r | 3 | A Martin | 6 | 3 | 2 | |||||||||||||||||||
| 3 | A Martin | 2 | 77 | 4 | Q | MT Barrios Vera | 3 | 4 | |||||||||||||||||||
| 7 | D Džumhur | 6 | 6 | Q | S Báez | 6 | 6 | ||||||||||||||||||||
| G Soeda | 4 | 3 | 7 | D Džumhur | 77 | 1 | 5 | ||||||||||||||||||||
| Q | S Báez | 6 | 6 | Q | S Báez | 65 | 6 | 7 | |||||||||||||||||||
| Q |  R Ramanathan | 4 | 0 | Q | S Báez | 3 | 6 | 6 | |||||||||||||||||||
 K Żuk | 4 | 6 | 6 | 2 | P Martínez | 6 | 3 | 4 | |||||||||||||||||||
 J Rodionov | 6 | 3 | 3 | K Żuk | 66 | 2 | |||||||||||||||||||||
| WC | N Serdarušić | 4 | 77 | 3 | 2 | P Martínez | 78 | 6 | |||||||||||||||||||
| 2 | P Martínez | 6 | 61 | 6 | |||||||||||||||||||||||
Filip Peliwo was the defending champion, but was no longer eligible to compete in junior tennis, and thus could not defend his title.
Kyle Edmund and Frederico Ferreira Silva were the defending champions, but were not eligible to compete this year.
This was the first edition of the tournament since 1991.
Thomaz Bellucci won the title, defeating João Sousa in the final, 7–6(7–4), 6–4.
Pedro Cachín was the defending champion but lost in the semifinals to Casper Ruud.
Kimmer Coppejans was the defending champion but lost in the first round to Tallon Griekspoor.
Dominic Thiem was the defending champion, but lost in the quarterfinals to Fernando Verdasco.
This was the first edition of the tournament.
Cedrik-Marcel Stebe was the defending champion but chose not to defend his title.
This was the first edition of the tournament.
Fabio Fognini was the defending champion, but chose not to defend his title.
João Sousa was the defending champion, but lost in the second round to David Goffin.
Juan Ignacio Londero was the defending champion, but lost to Laslo Đere in the quarterfinals.
Marco Cecchinato was the defending champion, but lost in the first round to Roberto Carballés Baena.
Fabio Fognini was the champion in 2014, when the event was last held, but chose to compete in Dubai instead.
Thiago Seyboth Wild was the defending champion but chose not to defend his title.
Reilly Opelka was the defending champion, but withdrew from the event.
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.
Miomir Kecmanović was the defending champion, but chose to compete at the Summer Olympics instead.
Jannik Sinner was the defending champion and successfully defended his title, defeating Gaël Monfils in the final, 6–3, 6–4.
Pedro Martínez defeated Sebastián Báez in the final, 4–6, 6–4, 6–4 to win the singles title at the 2022 Chile Open. It was his first ATP Tour title.