Mantellisaurus is a species of iguanodontid dinosaur from the Early Cretaceous of Europe. It is known from England, Belgium, and possibly Germany. It was originally believed to be a species of Iguanodon. However, a closer look at its skeleton in 2007 determined that it was its own genus. It is named in honor of Gideon Mantell, the original discoverer of Iguanodon.