| 2021 Amex-Istanbul Challenger II | |
|---|---|
| Date | 13–19 September |
| Edition | 35th |
| Surface | Hard |
| Location | Istanbul, Turkey |
| Champions | |
| Singles | |
 James Duckworth | |
| Doubles | |
 Radu Albot / Alexander Cozbinov | |
The 2021 Amex-Istanbul Challenger II was a professional tennis tournament played on hard courts. It was the 35th edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Istanbul, Turkey between 13 and 19 September 2021.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
| AUS | James Duckworth | 68 | 1 |
| MDA | Radu Albot | 108 | 2 |
 COL | Daniel Elahi Galán | 110 | 3 |
 JPN | Yasutaka Uchiyama | 123 | 4 |
| AUS | Marc Polmans | 148 | 5 |
 RUS | Evgeny Donskoy | 152 | 6 |
 UKR | Illya Marchenko | 154 | 7 |
 EGY |
The following players received wildcards into the singles main draw:
The following players received entry from the qualifying draw:
Nick Chappell 
Christopher Heyman
Laurent Lokoli 
Aldin Šetkić The following player received entry as a lucky loser:
James Duckworth def. 
Wu Tung-lin 6–4, 6–2. Radu Albot / Alexander Cozbinov def. 
Antonio Šančić / 
Artem Sitak 4–6, 7–5, [11–9].The 2016 Amex-Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 29th edition of the tournament which was part of the 2016 ATP Challenger Tour. It took place in Istanbul, Turkey between 12 and 18 September 2016.
The 2017 Amex-Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 30th edition of the tournament which was part of the 2017 ATP Challenger Tour. It took place in Istanbul, Turkey between 11 and 17 September 2017.
The 2018 Amex-Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 31st edition of the tournament which was part of the 2018 ATP Challenger Tour. It took place in Istanbul, Turkey between 10 and 16 September 2018.
The 2019 Amex-Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 32nd edition of the tournament which was part of the 2019 ATP Challenger Tour. It took place in Istanbul, Turkey between 9 and 15 September 2019.
The 2020 Amex-Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 33rd edition of the tournament which was part of the 2020 ATP Challenger Tour. It took place in Istanbul, Turkey between 19 and 25 October 2020.
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The 2021 Tenerife Challenger is a professional tennis tournament played on hard courts. It is the first edition of the tournament which is part of the 2021 ATP Challenger Tour. It will take place in Tenerife, Spain between 1 and 7 November 2021.
The 2021 Bahrain Ministry of Interior Tennis Challenger was a professional tennis tournament played on hard courts. It was the first edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Manama, Bahrain between 22 and 28 November 2021.
The 2021 Città di Forlì II was a professional tennis tournament played on hard courts. It was the first edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Forlì, Italy between 29 November and 5 December 2021.
