Quaesitosaurus, which translates to "extraordinary lizard," is a genus of nemegtosaurid sauropod. This genus consists solely of its type species, Q. orientalis, which was first described in 1983. It thrived during the Late Cretaceous epoch, approximately 72 to 71 million years ago, within the Barun Goyot Formation.

The skull of Quaesitosaurus is quite distinctive. It possesses an elongated, low, and somewhat horse-like structure with peg-like teeth positioned towards the front of the skull. This skull resemblance to those of Diplodocus and similar sauropods has led experts to make educated guesses about the rest of its body, suggesting it may have shared similarities with diplodocids.

Quaesitosaurus falls into the category of large-sized titanosaurs, with an estimated length of approximately 12 meters (about 39 feet), based on comparisons with its relatives. The skull of Quaesitosaurus, while intriguing, is not as complete as that of Nemegtosaurus, another titanosaur that is also known only from isolated skull material found in Mongolia. Like Nemegtosaurus and Rapetosaurus, the skull exhibits an elongated structure that juts forward, with nasal openings situated high on the skull, aligning with the eye socket. Additionally, the tooth crowns are notably long and slender.