Amazonsaurus (/ˌæməzənˈsɔːrəs/ AM-ə-zən-SOR-əs, 'Amazon lizard') is a genus of diplodocoid sauropod dinosaur from the Early Cretaceous Period of what is now South America.

[1] Fossils of Amazonsaurus, including some back and tail vertebrae, ribs, and fragments of the pelvis, are the only dinosaur remains identifiable at the generic level from the Itapecuru Formation of Maranhão.

This geologic formation dates back to the Aptian through Albian epochs of the Early Cretaceous Period, or about 125 to 100 million years ago.

[2] The tall neural spines on the tail vertebrae identify Amazonsaurus as a diplodocoid sauropod, but the fragmentary nature of the only known specimen makes it difficult to place A. maranhensis more specifically within the superfamily Diplodocoidea.

[2] Basal diplodocoids are found in several parts of South America, as well as northern Africa, during the Early Cretaceous, as are titanosaurian sauropods, and the carcharodontosaurid and spinosaurid theropods.