| Date: | 20–26 September |
| Edition: | 1st |
| Surface: | Clay |
| Location: | Ambato, Ecuador |
| Champs: |  Thiago Agustín Tirante |
| Champd: |  Diego Hidalgo /  Cristian Rodríguez |
The 2021 Ambato La Gran Ciudad was a professional tennis tournament played on clay courts. It was the 1st edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Ambato, Ecuador between 20 and 26 September 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Peru | Juan Pablo Varillas | 122 | 1 | |
 Slovakia | Andrej Martin | 123 | 2 | |
 Bolivia, Plurination;al State of | ||||
| Ecuador | Emilio Gómez | 156 | 4 | |
| Argentina | Renzo Olivo | 207 | 5 | |
| Argentina | Juan Pablo Ficovich | 247 | 6 | |
| Argentina | Thiago Agustín Tirante | 267 | 7 | |
 Bosnia and Herzegovina | Mirza Bašić | 269 | 8 |
The following players received wildcards into the singles main draw:
Daniel Espín Pérez Diego Hidalgo Antonio Cayetano MarchThe following player received entry into the singles main draw using a protected ranking:
The following player received entry into the singles main draw as a special exempt:
The following players received entry from the qualifying draw:
Alejandro Gómez
Patrick Kypson
Pol Martín Tiffon Matías ZukasThe following players received entry as lucky losers:
Alexis Gautier Alejandro GonzálezSee main article: 2021 Ambato La Gran Ciudad – Singles.
Thiago Agustín Tirante def. Juan Pablo Varillas 7–5, 7–5.See main article: 2021 Ambato La Gran Ciudad – Doubles.
Diego Hidalgo / Cristian Rodríguez def. Alejandro Gómez / Thiago Agustín Tirante 6–3, 4–6, [10–3].