| Named By: | Kurzanov and Bannikov in 1983 |
| Time Period: | Late Cretaceous, 85-70 Ma |
| Location: | Mongolia - Barun Goyot Formation |
| Size: | Uncertain due to incomplete fossil material |
| Diet: | Herbivore |
| Fossil(s): | Partial skull |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropoda | Titanosauroidea | Nemegtosauridae | |
Quaesitosaurus (meaning "extraordinary lizard") is a genus of titanosaurian sauropod found by Kurzanov and Bannikov in 1983. The type species is Quaesitosaurus orientalis. It lived from 85 to 70 million years ago during the Late Cretaceous (Santonian to Campanian ages). Its fossils, consisting solely of a partial skull, were found in the Barun Goyot Formation near Shar Tsav, Mongolia. Long, low and horse-like with frontally located peg-teeth, it is similar enough to the skulls of Diplodocus and its kin to have prompted informed speculation that the missing body was formed like those of diplodocids.
It is possible that Nemegtosaurus, also known from only skull material, is a very close relative of Quaesitosaurus, if not indeed a variation of the same animal.