Phuwiangosaurus (meaning "Phu Wiang lizard") is a genus of titanosaur dinosaur from the Early Cretaceous (Valanginian-Hauterivian) Sao Khua Formation of Thailand.

The type species, P. sirindhornae, was described by Martin, Buffetaut, and Suteethorn in a 1993 press release[1] and was formally named in 1994.

The type specimen of Phuwiangosaurus sirindhornae was discovered in Phu Wiang National Park in 1982, and excavated and prepared over the next several years.

The specimen was described as representing a new genus and species, Phuwiangosaurus sirindhornae, by Valérie Martin, Eric Buffetaut, and Varavudh Suteethorn in 1994.

[20][23] The Sao Khua Formation, where fossils of Phuwiangosaurus have been found, was deposited 133.6 to 132.1 million years ago, and represents a floodplain environment in a humid, subtropical climate.

[24] The Sao Khua dinosaur assemblage includes the large theropods Siamotyrannus, Phuwiangvenator, Vayuraptor, and Siamosaurus, and the ornithomimosaur Kinnareemimus.

[6] Ornithischian dinosaurs are not known from the Sao Khua Formation, although they are known from roughly contemporary environments in other parts of Asia.