| Named By: | Kobayashi & Azuma in 2003 |
| Time Period: | Early Cretaceous, Barremian |
| Location: | Japan, Honshu Island, Fukui Prefecture, Kitadani Formation |
| Size: | Approximately 4.5 meters long |
| Diet: | Herbivore |
| Fossil(s): | Several known specimens of partial remains |
| Classification: | | Chordata | Reptilia | Dinosauria | Ornithischia | Ornithopoda | Iguanodontia | Hadrosauroidea | |
Fukuisaurus (meaning "Fukui lizard") is a genus of herbivorous dinosaur from the Early Cretaceous. It was an ornithopod which lived in what is now Japan.
Remains of Fukuisaurus were discovered in 1989, in the Kitadani formation in Katsuyama, Fukui Prefecture, in rocks from the Kitadani Formation, dating to the Barremian. The type species, Fukuisaurus tetoriensis, was described in 2003 by Yoshitsugu Kobayashi and Yoichi Azuma. The genus name refers to Fukui; the specific name to the geological Tetori Group. The type specimens or cotypes are FPDM-V-40-1, a right maxilla, and FPDM-V-40-2, a right jugal. Further elements of a skull and a right sternal plate had been recovered. Since 2003 much more extensive finds have been made and much of the skeleton is now known.
Fukuisaurus is a relatively small species. In 2010 Gregory S. Paul estimated the length at 4.5 metres, the weight at four hundred kilograms. Being a bipedal, optionally quadrupedal, animal, it was similar in general build to Iguanodon, Ouranosaurus and Altirhinus. According to the describers Fukuisaurus was exceptional in that its skull was not kinetic: the tooth-bearing maxilla would be so strongly fused to the vomer that a sideways chewing motion would have been impossible.
A cladistic analysis showed that Fukuisaurus was a basal member of the Hadrosauroidea, less derived than Altirhinus.