The 2018 Challenger ATP Cachantún Cup was a professional tennis tournament played on red clay courts. It was the 11th edition of the tournament which was part of the 2018 ATP Challenger Tour. It took place in Santiago, Chile between 5 and 10 March 2018.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Gastão Elias | 102 | 1 | ||
 Italy | Marco Cecchinato | 103 | 2 | |
 Brazil | Rogério Dutra Silva | 106 | 3 | |
| Pedro Sousa | 121 | 4 | ||
 Slovakia | Andrej Martin | 124 | 5 | |
| Brazil | Thiago Monteiro | 125 | 6 | |
 Argentina | ||||
| Brazil | Thomaz Bellucci | 132 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
Facundo Argüello Pedro Cachin
Carlos Gómez-Herrera Gian Marco MoroniThe following players received entry as lucky losers:
See main article: 2018 Challenger ATP Cachantún Cup – Singles.
Marco Cecchinato def. Carlos Gómez-Herrera 1–6, 6–1, 6–1.See main article: 2018 Challenger ATP Cachantún Cup – Doubles.
Jonathan Eysseric def. Guido Andreozzi / Guillermo Durán 7–6(7–4), 1–6, [12–10].