# 1981 South American Championships – Singles

José Luis Clerc was the defending champion but did not compete that year.
Ivan Lendl won in the final 6–2, 6–2 against Guillermo Vilas.

## Seeds

A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated.
* Ivan Lendl (champion)
* Guillermo Vilas (final)
* Víctor Pecci (first round)
* Hans Gildemeister (second round)
* Rolf Gehring (quarterfinals)
* Jose Luis Damiani (second round)
* José Higueras (second round)
* Andrés Gómez (quarterfinals)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking
| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | I Lendl | 6 | 6 | | | | | | | | | | | | | | | | | | | |
| | Á Giménez | 3 | 4 | | 1 | I Lendl | 6 | 6 | | | | | | | | | | | | | | |
| | M Orantes | 6 | 6 | | | M Orantes | 4 | 0 | | | | | | | | | | | | | | |
| | M Hocevar | 2 | 3 | | | | | | | 1 | I Lendl | 6 | 7 | | | | | | | | | |
| | D Pérez | 6 | 6 | | | | | | | | D Pérez | 4 | 5 | | | | | | | | | |
| Q | H Roverano | 3 | 3 | | | D Pérez | 2 | 6 | 6 | | | | | | | | | | | | | |
| | P Arraya | 2 | 5 | | 6 | J L Damiani | 6 | 2 | 4 | | | | | | | | | | | | | |
| 6 | J L Damiani | 6 | 7 | | | | | | | | | | | | 1 | I Lendl | 7 | 6 | | | | |
| 3 | V Pecci | 7 | 3 | 1 | | | | | | | | | | | | P Rebolledo | 5 | 0 | | | | |
| | P Rebolledo | 5 | 6 | 6 | | P Rebolledo | 6 | 6 | | | | | | | | | | | | | | |
| | R Ycaza | 6 | 6 | | | R Ycaza | 1 | 1 | | | | | | | | | | | | | | |
| | E Bengoechea | 4 | 4 | | | | | | | | P Rebolledo | 6 | 6 | | | | | | | | | |
| | J López-Maeso | 6 | 7 | | | | | | | 8 | A Gómez | 1 | 0 | | | | | | | | | |
| | G Aubone | 4 | 5 | | | J López-Maeso | 5 | 2 | | | | | | | | | | | | | | |
| Q | B Prajoux | 1 | 2 | | 8 | A Gómez | 7 | 6 | | | | | | | | | | | | | | |
| 8 | A Gómez | 6 | 6 | | | | | | | | | | | | | | | | 1 | Ivan Lendl | 6 | 6 |
| 7 | J Higueras | 6 | 3 | 6 | | | | | | | | | | | | | | | 2 | Guillermo Vilas | 2 | 2 |
| | G Urpí | 2 | 6 | 4 | 7 | J Higueras | 3 | 1 | | | | | | | | | | | | | | |
| | A Maurer | 1 | 6 | 7 | | A Maurer | 6 | 6 | | | | | | | | | | | | | | |
| | K Eberhard | 6 | 1 | 5 | | | | | | | A Maurer | 7 | 6 | | | | | | | | | |
| | J Aguilera | 6 | 6 | | | | | | | Q | J Aguilera | 5 | 1 | | | | | | | | | |
| | J Soares | 1 | 2 | | Q | J Aguilera | 2 | 6 | 7 | | | | | | | | | | | | | |
| | F Luna | 4 | 7 | 0 | 4 | H Gildemeister | 6 | 0 | 5 | | | | | | | | | | | | | |
| 4 | H Gildemeister | 6 | 6 | 6 | | | | | | | | | | | | A Maurer | 4 | 4 | | | | |
| 5 | R Gehring | 1 | 6 | 6 | | | | | | | | | | | 2 | G Vilas | 6 | 6 | | | | |
| | B Boileau | 6 | 3 | 4 | 5 | R Gehring | 7 | 7 | | | | | | | | | | | | | | |
| | J Fillol | 6 | 6 | | | J Fillol | 6 | 6 | | | | | | | | | | | | | | |
| | F González | 2 | 3 | | | | | | | 5 | R Gehring | 7 | 5 | 5 | | | | | | | | |
| | R Argüello | 6 | 6 | | | | | | | 2 | G Vilas | 5 | 7 | 7 | | | | | | | | |
| | G Tiberti | 2 | 3 | | | R Argüello | | | | | | | | | | | | | | | | |
| | R Cano | 4 | 6 | | 2 | G Vilas | | | | | | | | | | | | | | | | |
| 2 | G Vilas | 6 | 7 | | | | | | | | | | | | | | | | | | | |