| Named By: | V. Martin, E. Buffetaut & V. Sweethorn in 1994 |
| Time Period: | Early Cretaceous, 140-130 Ma |
| Location: | Thailand - Sao Khua Formation |
| Size: | Roughly about 12.2 meters long |
| Diet: | Herbivore |
| Fossil(s): | Holotype based upon partial but articulated remains. A second individual described in 2009 is preserved at around 60% completeness for the post cranial skeleton (including pelvis, rear leg bones, ribs and partial and complete vertebrae from the entire spinal column), as well as partial skull |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropoda | Titanosauria | Nemegtosauridae | |
Phuwiangosaurus (meaning "Phu Wiang lizard") is a genus of euhelopodid 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 1994; it was named to honour Princess Maha Chakri Sirindhorn of Thailand, who was interested in the geology and palaeontology of Thailand.
It was a mid-sized sauropod, measuring 15-20 m in length.
Phuwiangosaurus was originally assigned to Titanosauria, but D'Emic (2012, 2013), Mannion et al. (2013), and Mocho et al. (2014) have reclassified it outside Titanosauria in Euhelopodidae.