Any member of the genus Hadrosaurus or family Hadrosauridae, an extinct family of heavy bipedal partly aquatic dinosaurs with duck-billed skull and webbed feet; of the Upper Cretaceous in North America.

from the Greek, meaning "massive lizard;" a group of bird-hipped dinosaurs that lived during the Cretaceous period. Hadrosaurs had long, flat snouts, which accounts for their nickname “duck-billed,” and many also had crested skulls.

Usually refers to late Cretaceous duckbill dinosaurs belonging within ornithopoda and probably descended from the iguanodontids.