Camptosaurus (/ˌkæmptəˈsɔːrəs/ KAMP-tə-SOR-əs) is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America and possibly also Europe.

It was described by Charles Gilmore in 1909 based on the holotype and only known specimen USNM 4753, a fragmentary postcranium, by the "narrowness or depressed nature of the ilia".

[10] It differs from C. dispar in the lower jaw, shorter neck vertebrae, and straighter ischium ending in a small "foot" among other features.

C. inkeyi (Nopcsa, 1900) consists of fragmentary material, a dentary and articular from Upper Cretaceous rocks of the Haţeg Basin in Romania.

It was earlier believed to be a dubious dryosaurid,[14][12] but a more recent analysis contends that the diagnostic features of Dryosauridae do not overlap with its material, instead considering it an iguanodontian.

[14] The remaining European species Camptosaurus prestwichii was recovered from Chawley Brick Pits, Cumnor Hurst in Oxfordshire in England.

Cumnoria has been recovered as a styracosternan, more closely related to advanced iguanodonts than to Camptosaurus dispar, similar to the case of Uteodon.

[21] Museum curator John Foster describes them as having "thick median ridges on their lateral sides and denticles along their edges," these features were similar to, but "more fully developed" than those in Dryosaurus.

[21] Camptosaurus teeth frequently exhibit extensive wear, which indicates that individuals in the genus had a diet of relatively tough vegetation.

This would mean that the genus is closely related to the ancestor of later iguanodontid and hadrosaurid dinosaurs and was more derived than contemporaries such as Dryosaurus, Drinker, and Othnielosaurus.

[21] A tiny 9 inch fossilized embryo, referred to Camptosaurus, was retrieved from Morrison Formation strata at Dinosaur National Monument in Utah.