Guaibasaurus is an extinct genus of basal saurischian dinosaur known from the Late Triassic Caturrita Formation of Rio Grande do Sul, southern Brazil.

[9][10] Guaibasaurus was originally named on the basis of the holotype, MCN PV2355, a well-preserved partial postcranial skeleton and the paratype, MCN PV2356, an articulated and nearly complete left hindlimb, which were discovered in the "Sesmaria do Pinhal 2" locality near Candelária, Rio Grande do Sul, in Brazil, in the upper portion of the Candelária Sequence or the Caturrita Formation.

The referred materials were collected from the "Linha São Luiz" locality near the town of Faxinal do Soturno, Rio Grande do Sul, also in the upper portion of the Candelária Sequence or the Caturrita Formation.

All specimen were collected in these two localities from the lower portion of the Caturrita Formation (Rosário do Sul Group, Paraná Basin) or alternatively the uppermost Santa Maria 2 Sequence, dating to the early Norian faunal stage of the Late Triassic.

[13][14][15][16] An article depicting a novel phylogenetic hypothesis for silesaurids also recovers Guaibasaurus as a sauropodomorph, but close-related to the coeval Unaysaurus and Macrocollum, rather than early forms such as Saturnalia.