Aeolosaurus (/ˌiːoʊloʊˈsɔːrəs/; "Aeolus' lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America.

The holotype of Aeolosaurus rionegrinus consists of a series of seven tail vertebrae, as well as parts of both forelimbs and the right hindlimb.

It was discovered in the Angostura Colorada Formation in Argentina, which dates from the Campanian stage of the Late Cretaceous, about 83 to 74 million years ago.

A. rionegrinus was roughly 14 meters (46 ft) long and 6 tonnes (6.6 short tons) in weight according to Gregory S.

[11] The tail of Aeolosaurus was apparently curved strongly downward, a trait likely shared with other members of Aeolosaurini.

[3] The classification of Aeolosaurus and its relatives is heavily based on features of the tail vertebrae, which are the only bones preserved in most aeolosaurs.

The phylogeny of Aeolosaurini here is based on Gallina and Otero 2015, with the application of clade names according to their phylogenetic definitions.

This specimen is from the Allen Formation of Rio Negro, dating back about 70 to 68 million years ago to the middle Maastrichtian stage.

While this specimen bears features that characterize the genus Aeolosaurus, it is from a younger time period and shows enough differences that the authors recognized it as a possible second species.

Future discoveries may give scientists more information on variation within the genus, and show that all of the above specimens belong to A. rionegrinus, or that they merit being formally named.

A middle caudal vertebra from the Serra da Galga Formation, CPP 248, cannot be evaluated for any diagnostic features of the genus Aeolosaurus.

[4] However, because it clearly does not belong to Gondwanatitan, it is most likely that this vertebra represents Aeolosaurus, a genus otherwise unknown from the Serra da Galga Formation.

[2][13] Aeolosaurus lived during the Campanian and Maastrichtian ages of the Late Cretaceous and shared its environment with hadrosaurs.