Tangvayosaurus (meaning "Tang Vay lizard") is a genus of sauropod dinosaur from the Aptian-Albian age Lower Cretaceous Gres superieurs Formation of Savannakhet Province, Laos.

Allain et al. also referred the old species "Titanosaurus" falloti (Hoffet, 1942),[2] from the same formation and based on partial thigh bones and tail vertebrae, to their genus as T.

[3] The most recent review tentatively retains the genus because it is different from the only other established sauropod from the same approximate time but found next door in Thailand (Phuwiangosaurus), but disagrees with adding T. falloti to it.

It was initially assigned by Allain et al. (1999) to the Titanosauria, who noted strong affinities to Phuwiangosaurus, which they also considered a titanosaur.

[3] A more recent review by Suteethorn et al. (2010) resolved both Tangvayosaurus and Phuwiangosaurus as more basal titanosauriforms.