| Warsaw Formation | |
| Type: | Formation |
| Age: | Mississippian |
| Period: | Mississippian |
| Namedfor: | Warsaw, Hancock County, Illinois[1] |
| Region: | Illinois, Iowa, Missouri |
| Country: | United States |
| Underlies: | Salem Formation |
| Overlies: | Keokuk Limestone |
The Warsaw Formation is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian subperiod.