| 2025 Istanbul Challenger | |
|---|---|
| Date | 1–7 September |
| Edition | 39th |
| Surface | Hard |
| Location | Istanbul, Turkey |
| 2024 Champions | |
| Singles | |
 Damir Džumhur | |
| Doubles | |
 Aleksandre Bakshi /  Yankı Erel | |
The 2025 Istanbul Challenger was a professional tennis tournament played on hard courts. It was the 39th edition of the tournament which was part of the 2025 ATP Challenger Tour. It took place in Istanbul, Turkey between 1 and 7 September 2025.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 SVK | Lukáš Klein | 119 | 1 |
 FIN | Otto Virtanen | 123 | 2 |
 ESP | Martín Landaluce | 138 | 3 |
 FRA | |||
 TUN | Moez Echargui | 165 | 5 |
| FRA | Calvin Hemery | 185 | 6 |
| FRA | Hugo Grenier | 188 | 7 |
 LBN | Benjamin Hassan | 200 | 8 |
 MEX | Rodrigo Pacheco Méndez | 224 | 9 |
The following players received wildcards into the singles main draw:
Kaya Arınç Koray Kırcı Mert Naci Türker The following player received entry into the singles main draw using a protected ranking:
The following players received entry into the singles main draw as alternates:
The following players received entry from the qualifying draw:
Alex Hernández Michal Krajčí
Péter Makk
Ivan Nedelko 
Luca Potenza
Vadym Ursu vs. / vs. / 
