| Named By: | Ameghino in 1895 |
| Time Period: | Mid-Late Oligocene (Deseadan)~29.2-26.3 Ma |
| Location: | Argentina |
| Size: | Uncertain, but probably over 2 meters high |
| Diet: | Carnivore |
| Fossil(s): | Single specimen |
| Classification: | | Chordata | Aves | Cariamae | Phorusrhacidae | Brontornithinae | |
Physornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds", within the subfamily Brontornithinae, that lived in Argentina. The type species is P. fortis. It lived during the Middle to Late Oligocene (Deseadan). Fossils of Physornis have been found in strata of 29.2 to 26.3 million years old, belonging to the Sarmiento Formation.