| Named By: | Obruchev in 1964 |
| Time Period: | Middle to Late Devonian |
| Location: | Worldwide, including Australia - Gogo Formation, Canada, China, Iran, Poland, Russia, USA |
| Size: | Up to 3 meters long |
| Diet: | Carnivore/Piscivore |
| Fossil(s): | Many known specimens of the bony exoskeleton, some traces of soft tissue including circulatory structures (blood vessels), muscle fibres, and nerve tissue |
| Classification: | | Chordata | Palcodermi | Arthrodira | Dinichthyoidea | Dinichthyidae | |
| Also known as: | | Dinichthys pustulosus | |
Eastmanosteus ("Eastman's bone") is a fossil genus of dunkleosteid placoderms. It was closely related to the giant Dunkleosteus, but differed from that genus in size, in possessing a distinctive tuberculated bone ornament, a differently shaped nuchal plate and a more zig-zagging course of the sutures of the skull roof.
Species of Eastmanosteus had powerful jaws with sharp cutting edges and were likely active predators. Fossils have been found in many parts of the world in marine sediments dating from the Middle to Late Devonian. They were medium-to-large fish, with specimens E. pustulosus and E. licharevi approaching a total length of 3 metres. Complete exoskeletons with soft-tissue traces of E. calliaspis from Australia make this one of the best known dunkleosteids.