| Named By: | Joanne Kluessendorf & Peter Doyle in 2000 |
| Time Period: | Pennsylvanian |
| Location: | USA |
| Size: | Unavailable |
| Diet: | Carnivore |
| Fossil(s): | Preserved flat on a stone |
| Classification: | | Mollusca | Cephalopoda | Octopoda | |
Pohlsepia mazonensis is the earliest described octopod, dated at approximately 296 million years old. The species is known from a single exceptionally preserved fossil discovered in the Pennsylvanian Francis Creek Shale of the Carbondale Formation, north-east Illinois, United States.
Pohlsepia mazonensis is named after its discoverer, James Pohl, and the type locality, Mazon Creek. Its habitat was the shallows seawards of a major river delta in what at that time was an inland ocean between the Midwest and the Appalachians.
The type specimen is reposited at the Field Museum of Natural History in Chicago, Illinois.