Eucercosaurus (meaning "good-tailed lizard" ) is the name given to a genus of ornithopod dinosaur from the Albian stage of the Early Cretaceous. It was an ornithopod discovered in the Cambridge Greensand of England and is known from 19 centra, 3 sacrals, 4 dorsals and 12 caudals, and a neural arch found near Trumpington, Cambridgeshire. The type species, E. tanyspondylus, was described by British paleontologist Harry Seeley in 1879. It is considered a dubious name, and was once considered an ankylosaur. According to a 2020 study, Eucercosaurus and Syngonosaurus were basal iguanodontians.