Austroposeidon is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Presidente Prudente Formation of Brazil.

The specimen was discovered in the Campanian-Maastrichtian Presidente Prudente Formation of the Bauru Group by palaeontologist Llewellyn Ivor Price in an outcrop along the Raposo Tavares Road in 1953, but the remains were not described until 2016.

The specific name is the Latin word magnificus ("great, elevated, noble"), referring to the large size of the specimen.

[1] Austroposeidon was a large sauropod, the largest dinosaur discovered in Brazil, with the only known specimen, an adult, having a length of about 25 metres (82 ft).

[2] Andesaurus Rukwatitan Malawisaurus Puertasaurus Austroposeidon Mendozasaurus Futalognkosaurus Quetecsaurus Isisaurus Epachthosaurus Pellegrinisaurus Maxakalisaurus Tapuiasaurus Trigonosaurus Lirainosaurus Ampelosaurus Bonitasaura Dreadnoughtus Alamosaurus Opisthocoelicaudia Neuquensaurus Rocasaurus Saltasaurus Rapetosaurus Brasilotitan Uberabatitan Aeolosaurus maximus Muyelensaurus Rinconsaurus Overosaurus Gondwanatitan Aeolosaurus colhuehuapensis Aeolosaurus rionegrinus In 2022, Austroposeidon was recovered as a member of Lognkosauria by Navarro et al.:[3] BIBE 45854 (cf.