| Named By: | Mario A. Hunicken in 1980 |
| Time Period: | Gzhelian~306.9-298.9 Ma |
| Location: | South America, Argentina |
| Size: | Reconstructed as a eurypterid, length estimated to be about 54 centimetres long |
| Diet: | unavailable |
| Fossil(s): | Two specimens of partial remains |
| Classification: | | Arthropoda | Merostomata | Eurypterida | Hibbertopteroidea | Mycteroptidae | |
Megarachne is an extinct genus of eurypterids, found in Late Carboniferous (Pennsylvanian Gzhelian)-aged freshwater strata in San Luis, Argentina. The type species of the genus is M. servinei.