| Named By: | Romer & Price in 1940 |
| Time Period: | Early Permian |
| Location: | USA, New Mexico, Ohio |
| Size: | Uncertain due to lack of remains |
| Diet: | Carnivore |
| Fossil(s): | Partial maxillas and vertebrae |
| Classification: | | Chordata | Synapsida | Ophiacodontidae | |
Baldwinonus is an extinct genus of basal synapsid from the Early Permian. The type species is Baldwinonus trux, named in 1940 from the Cutler Formation of New Mexico. A second species, Baldwinonus dunkardensis, was named in 1952 from Ohio. Baldwinonus was first classified in the family Eothyrididae, but the group has since been recognized as a wastebasket taxon for many early synapsids. More recently, Baldwinonus has been placed in the family Ophiacodontidae. Its phylogenetic relationship to other early synapsids remains poorly understood because it is only known from a few fragments of bone.