Hadrosaurus is a genus of hadrosaurid ornithopod dinosaurs that lived in North America during the Late Cretaceous Period in what is now the Woodbury Formation in New Jersey about 83.6 to 77.9 million years ago. The holotype specimen was found in fluvial marine sedimentation, meaning that the corpse of the animal was transported by a river and washed out to sea. Some fossils are found in the Tar Heel/Coachman Formation.