Triunfosaurus (meaning "Triunfo Basin reptile") is a genus of somphospondylan sauropod dinosaur from the Early Cretaceous of Brazil.

[1] The holotype of Triunfosaurus, UFRJ-DG 498, was found in a sandstone layer of the Rio Piranhas Formation to the west of Paraíba State, Brazil.

Study of pollen found in the Rio Piranhas itself supports a Berriasian-Valanginian age, although the presence of Hauterivian deposits cannot be ruled out.

[1] In 2017, Triunfosaurus was placed in the clade Titanosauria as defined by Wilson and Upchurch in 2003,[4] which is supported by the articulations of its haemal arches having two distinct surfaces as in other titanosaurs.

[1] Andesaurus delgadoi Mendozasaurus neguyelap Malawisaurus dixleyi Epachthosaurus sciuttoi Argentinosaurus huinculensis Malarguesaurus florenciae Triunfosaurus leonardii Nemegtosaurus mongoliensis Rapetosaurus krausei Tapuiasaurus macedoi Isisaurus colberti Trigonosaurus pricei Alamosaurus sanjuanensis Opisthocoelicaudia skarzynskii Saltasaurus loricatus Neuquensaurus australis This topology is poorly supported, since forcing Triunfosaurus to nest outside of the Titanosauria would require only two additional evolutionary steps, and the support values obtained for the clades are also low.

As the oldest basal titanosaurian found to date, Triunfosaurus was initially used to support the hypothesis that the wider group originated on the supercontinent Gondwana around the Hauterivian, more specifically within South America.

[1][10] In a subsequent redescription of the somphospondylan Austrosaurus, Steven Poropat and colleagues raised a number of objections to the titanosaurian status of Triunfosaurus.

Features in these vertebrae that are unusual for middle caudal vertebrae include the prominent transverse processes bearing deep diapophyses (articulations with the ribs), the pronounced prezygodiapophyseal laminae connecting the prezygapophyses and transverse processes, the well-developed spinoprezygapophyseal laminae connecting the prezygapophyses and neural spines, the deep indentations on the outer margins of the bottom of the centra, and the postzygapophyseal facet joints extending backwards from the midpoint of the side of the centra.

For these reasons, Poropat et al. reassigned Triunfosaurus to the Somphospondyli, being unable to confidently support its titanosaurian affinities due to its problematic nature.