| Named By: | Othniel Charles Marsh in 1878 |
| Time Period: | Upper Jurassic, Upper Cretaceous |
| Location: | USA, Wyoming - Morrision Formation. Canada, Alberta |
| Size: | Uncertain |
| Diet: | Herbivore |
| Fossil(s): | Very partial and fragmentary remains |
| Classification: | | Chordata | Reptilia | Dinosauria | Ornithischia | Ornithopoda | Hypsilophodontidae | |
Laosaurus (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species is Laosaurus celer, first described by O.C. Marsh in 1878 from remains from the Oxfordian-Tithonian-age Upper Jurassic Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous of Alberta, Laosaurus minimus, are also considered dubious.