Quaesitosaurus is a genus of nemegtosaurid sauropod containing only the type species, Q. orientalis, described in 1983. It lived from 72 to 71 million years ago during the Late Cretaceous epoch in the Barun Goyot Formation. With long, low and horse-like with frontally located peg-teeth, the skull of Quaesitosaurus is similar enough to the skull of Diplodocus and its kin to have prompted informed speculation that the missing body was built like those of diplodocids.

Nemegtosauridae is a family of titanosaurian sauropod dinosaurs based on their diplodocid-like skulls. Only three species are known: Nemegtosaurus, Quaesitosaurus and possibly Tapuiasaurus, each from the Cretaceous.