Augustasaurus is an extinct genus of sauropterygians that lived during the Anisian stage of the Middle Triassic in what is now North America.

Its postcranial anatomy is similar to that of future plesiosaurs, with which it visibly shares a common ancestor according to the most recent phylogenetic analyses.

It was excavated in the Fossil Hill Member of the Favret Formation, a site dating from the Late Anisian to the Middle Triassic.

After analysis, paleontologists Paul Martin Sander [de], Olivier Cedric Rieppel and Hugo Bucher established it as the holotype of a new genus and species under the name Augustasaurus hagdorni.

The skull's elongated rostrum tapers to a dull point, the anterior premaxillary and maxillary teeth have been described as "fang-like", and the squamosal makes a box-like suspensorium.

[7][8] Early descriptions placed Augustasaurus in the proposed family Pistosauridae, classified as a sister taxon to the type genus Pistosaurus.

[3] The most abundant marine reptiles of the Fossil Hill Member are the ichthyosaurs, including the apex predator Thalattoarchon, Phalarodon, Omphalosaurus and the large Cymbospondylus.