| Named By: | Frederick A. Lucas in 1902 |
| Time Period: | Early Cretaceous, 130 Ma |
| Location: | USA, South Dakota - Lakota Formation |
| Size: | Uncertain due to incomplete remains, but possibly up to 1.2 meters tall at the hips |
| Diet: | Herbivore |
| Fossil(s): | Partial post cranial remains |
| Classification: | | Chordata | Reptilia | Dinosauria | Ornithischia | Thyreophora | Ankylosauria | Nodosauridae | Polacanthinae | |
| Also known as: | | Stegosaurus marshi | |
Hoplitosaurus (meaning "Hoplite lizard") was a genus of armored dinosaur related to Polacanthus. It was named from a partial skeleton found in the ?Barremian-age Lower Cretaceous Lakota Formation of Custer County, South Dakota. It is an obscure genus which has been subject to some misinterpretation of its damaged remains. Although there was a push to synonymize it with Polacanthus in the late 1980s-early 1990s, Hoplitosaurus has been accepted as a valid albeit poorly known genus in more recent reviews.