| Named By: | Andrew T. McDonald in 2011 |
| Time Period: | Early Cretaceous, 137 Ma |
| Location: | USA, South Dakota - Lakota Formation, Chilson Member |
| Size: | Precise size uncertain due to lack of remains, but estimated to be in the region of about 4-5 meters long |
| Diet: | Herbivore |
| Fossil(s): | Post cranial remains, specifically an ilium and some vertebrae |
| Classification: | | Chordata | Reptilia | Dinosauria | Ornithischia | Ornithopoda | Iguanodontia | |
| Also known as: | | Camptosaurus depressus | Planicoxa depressa | |
Osmakasaurus is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the lower Cretaceous period (Valanginian age) in what is now Buffalo Gap of South Dakota, United States. It is known from the Chilson Member of the Lakota Formation. This genus was named by Andrew T. McDonald in 2011 and the type species is Osmakasaurus depressus. O. depressus was previously referred to as Camptosaurus depressus, and was first described in 1909 by Charles W. Gilmore.