| Named By: | John William Dawson in 1860 |
| Time Period: | Pennsylvanian, 312 Ma |
| Location: | Canada, Nova Scotia |
| Size: | 20 centimetres long |
| Diet: | unavailable |
| Fossil(s): | Several specimens, fossilised footprints found in New Brunswick |
| Classification: | | Chordata | Reptilia | Captorhinida | Protorothyrididae | |
Hylonomus (hylo- "forest" + nomos "dweller") is an extinct genus of reptile that lived 312 million years ago during the Late Carboniferous period. It is the earliest unquestionable reptile (Westlothiana is older, but in fact it may have been an amphibian, and Casineria is rather fragmentary). The only species is the type species Hylonomous lyelli.