Protohadros is a genus of medium to large ornithopod dinosaur that lived in North America during the late Cretaceous. Protohadros means ‘first hadrosaur)’, and reflects the idea at the time of its description that the genus may represent the earliest true hadrosaur in North America. However, scientific opinion has since changed and it is now regarded as a non-hadrosaurid iguanodontian, a basal member of the Hadrosauroidea, though one closely related to the Hadrosauridae.
Due to the paucity of the remains, much of the reconstruction of this dinosaur is speculative. Head speculated that the remains found were that of a subadult and that fully-grown individuals could have been larger. It is thought due to the nature of the animal's skull its diet would then have consisted of the swamp plants which grew in the delta streams in its habitat, scooped up by the broad, down-turned mouth. In some respects, Protohadros was intermediate in morphology to more derived hadrosaurids. Like these, it did have pleurokinesis, a cranial joint system that produced the food-grinding action, but only partially in that the quadrate at the back of the skull was still relatively immobile.