| Singles | |
|---|---|
| 2020 Amex-Istanbul Challenger | |
| Champion |  Ilya Ivashka |
| Runner-up |  Martin Kližan |
| Score | 6–1, 6–4 |
Ugo Humbert was the defending champion [1] but chose not to defend his title.
Ilya Ivashka won the title after defeating Martin Kližan 6–1, 6–4 in the final.
Pedro Martínez (withdrew) Jaume Munar (second round)
Taro Daniel (first round)
Evgeny Donskoy (first round, retired)
Jason Jung (quarterfinals)
Lorenzo Giustino (first round) Ilya Ivashka (champion)
Mohamed Safwat (first round)| Semifinals | Final | ||||||||||||
| Martin Kližan | 6 | 7 | |||||||||||
| Q |  Borna Gojo | 4 | 5 | ||||||||||
| Martin Kližan | 1 | 4 | |||||||||||
| 7 | Ilya Ivashka | 6 | 6 | ||||||||||
 Benjamin Bonzi | 6 | 2 | 3 | ||||||||||
| 7 | Ilya Ivashka | 3 | 6 | 6 | |||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| LL | A Vatutin | 6 | 3 | 1 | |||||||||||||||||||||||
| Q | N Serdarušić | 4 | 6 | 6 | Q | N Serdarušić | 69 | 3 | |||||||||||||||||||
| Q |  M McDonald | 6 | 6 | Q | M McDonald | 711 | 6 | ||||||||||||||||||||
| LL | T Gabashvili | 4 | 1 | Q | M McDonald | 6 | 4 | 3 | |||||||||||||||||||
 I Marchenko | 66 | 3 | M Kližan | 4 | 6 | 6 | |||||||||||||||||||||
| M Kližan | 78 | 6 | M Kližan | 77 | 6 | ||||||||||||||||||||||
| R Marcora | 78 | 6 | R Marcora | 63 | 1 | ||||||||||||||||||||||
| 8 | M Safwat | 66 | 0 | M Kližan | 6 | 7 | |||||||||||||||||||||
| 3 | T Daniel | 6 | 64 | 63 | Q | B Gojo | 4 | 5 | |||||||||||||||||||
| Q | B Gojo | 2 | 77 | 77 | Q | B Gojo | 65 | 7 | 6 | ||||||||||||||||||
| S Stakhovsky | 4 | 0 |  J Clarke | 77 | 5 | 2 | |||||||||||||||||||||
| J Clarke | 6 | 6 | Q | B Gojo | 6 | 1 | |||||||||||||||||||||
 S Ofner | 67 | 6 | 6 | S Ofner | 3 | 0r | |||||||||||||||||||||
| WC |  M İlhan | 79 | 4 | 4 | S Ofner | 4 | 7 | 6 | |||||||||||||||||||
| WC | A Çelikbilek | 6 | 6 | WC | A Çelikbilek | 6 | 5 | 3 | |||||||||||||||||||
| 6 | L Giustino | 0 | 3 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 5 | J Jung | 2 | |||||||||||||||||||||||||
 D Istomin | 2r | 5 | J Jung | 6 | 6 | ||||||||||||||||||||||
| Q | T Lamasine | 4 | 6 | 7 | Q | T Lamasine | 0 | 3 | |||||||||||||||||||
 P Polansky | 6 | 2 | 5 | 5 | J Jung | 66 | 2 | ||||||||||||||||||||
 E Gómez | 4 | 78 | 5 | B Bonzi | 78 | 6 | |||||||||||||||||||||
| M Janvier | 6 | 66 | 7 | M Janvier | 2 | 5 | |||||||||||||||||||||
| B Bonzi | 6 | 4 | B Bonzi | 6 | 7 | ||||||||||||||||||||||
| 4 | E Donskoy | 2 | 1r | B Bonzi | 6 | 2 | 3 | ||||||||||||||||||||
| 7 | I Ivashka | 6 | 6 | 7 | I Ivashka | 3 | 6 | 6 | |||||||||||||||||||
| WC | E Kırkın | 2 | 4 | 7 | I Ivashka | 6 | 6 | ||||||||||||||||||||
| E Benchetrit | 4 | 3 | C İlkel | 2 | 2 | ||||||||||||||||||||||
| C İlkel | 6 | 6 | 7 | I Ivashka | 6 | 6 | |||||||||||||||||||||
 F Ferreira Silva | 2 | 63 |  D Popko | 4 | 0 | ||||||||||||||||||||||
| D Popko | 6 | 77 | D Popko | 6 | 6 | ||||||||||||||||||||||
 E Ymer | 3 | 3 | 2 | J Munar | 3 | 4 | |||||||||||||||||||||
| 2 | J Munar | 6 | 6 | ||||||||||||||||||||||||
Radu Albot was the defending champion but chose not to defend his title.
Yūichi Sugita was the defending champion but chose not to defend his title.
Borna Ćorić was the defending champion, but withdrew before the tournament began.
Henri Kontinen and John Peers were the defending champions, but lost in the first round to Juan Sebastián Cabal and Robert Farah.
Damir Džumhur was the defending champion, but lost in the quarterfinals to Stan Wawrinka.
Jo-Wilfried Tsonga was the defending champion, but lost in the second round to Gaël Monfils.
Roberto Bautista Agut was the defending champion, but lost in the second round to Nikoloz Basilashvili.
Ilya Ivashka was the defending champion but chose not to defend his title.
Dominic Thiem was the defending champion, but chose to compete in the Laver Cup instead.
Stefanos Tsitsipas was the defending champion and successfully defended his title, defeating Félix Auger-Aliassime in the final, 6–3, 6–4.
The tournament was played on a hard surface. Due to the ongoing COVID-19 pandemic and many ATP tournaments having been cancelled, this year's event was upgraded to ATP 500 level.
Divij Sharan and Igor Zelenay were the defending champions, but both players chose not to participate. Sharan is instead participating at the Cologne tournament and Zelenay at the Sardinia tournament.
Jannik Sinner was the defending champion but chose not to defend his title.
Ilya Ivashka was the defending champion but chose not to defend his title.
Alexander Zverev was the defending champion from when the event was held in 2019, but chose not to defend his title.
Marin Čilić defeated Félix Auger-Aliassime in the final, 7–6(7–2), 6–3 to win the singles tennis title at the 2021 Stuttgart Open. It was Čilić's 19th career ATP Tour singles title, his first in three years, and he did not drop a set en route to the victory. The No. 47-ranked, 32-year-old Čilić also became the lowest-ranked winner since Juan Carlos Ferrero in 2011 and the third-oldest champion in tournament history. Defending finalist Auger-Aliassime was contesting for his first career singles title in his eighth final.
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.
Ilya Ivashka was the defending champion but chose not to defend his title.
Adrian Mannarino defeated Laslo Đere in the final, 7–6(7–1), 6–4 to win the singles tennis title at the 2022 Winston-Salem Open. Mannarino saved four match points en route to the title, in his first-round match against Christopher O'Connell.
Andrey Rublev defeated Holger Rune in the final, 5–7, 6–2, 7–5 to win the men's singles tennis title at the 2023 Monte-Carlo Masters. It was his first ATP Tour Masters 1000 title. 19-year-old Rune became the first teenager to reach the Monte-Carlo Masters final since Rafael Nadal in 2006.