| Date: | 26 July – 1 August |
| Edition: | 2nd |
| Surface: | Clay |
| Location: | Trieste, Italy |
| Champs: |  Tomás Martín Etcheverry |
| Champd: |  Orlando Luz / Felipe Meligeni Alves |
The 2021 Internazionali di Tennis Città di Trieste was a professional tennis tournament played on clay courts. It was the 2nd edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Trieste, Italy between 26 July and 1 August 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Bosnia and Herzegovina | Damir Džumhur | 127 | 1 | |
 France | Antoine Hoang | 143 | 2 | |
| Argentina | Tomás Martín Etcheverry | 166 | 3 | |
 Serbia | ||||
 Italy | Alessandro Giannessi | 177 | 5 | |
| Argentina | Marco Trungelliti | 192 | 6 | |
| Maximilian Marterer | 196 | 7 | ||
| Italy | Thomas Fabbiano | 202 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw using a protected ranking:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
See main article: 2021 Internazionali di Tennis Città di Trieste – Singles.
Tomás Martín Etcheverry def. Thiago Agustín Tirante 6–1, 6–1.See main article: 2021 Internazionali di Tennis Città di Trieste – Doubles.
Orlando Luz / Felipe Meligeni Alves def. Antoine Hoang / Albano Olivetti 7–5, 6–7(6–8), [10–5].
