| Merrimac, Illinois | |
| Settlement Type: | Unincorporated community |
| Etymology: | Meramec River |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Illinois |
| Subdivision Type2: | County |
| Subdivision Name2: | Monroe |
| Subdivision Type3: | Precinct |
| Subdivision Name3: | 15 |
| Pushpin Map: | Illinois#USA |
| Pushpin Label: | Merrimac |
| Coordinates: | 38.3708°N -90.3333°W |
| Elevation Ft: | 404 |
| Population Density Km2: | auto |
| Timezone1: | CST |
| Utc Offset1: | -6 |
| Timezone1 Dst: | CDT |
| Utc Offset1 Dst: | -5 |
| Postal Code Type: | Postal code |
| Postal Code: | 62295 |
| Area Code: | 618 |
Merrimac, Illinois is a small unincorporated community in the historic Moredock Precinct of Monroe County, Illinois, United States. It is located in the American Bottoms, adjacent to the Mississippi River levee due south of that river's confluence with the Meramec. It takes its name from this river whose name was translated as 'Ugly Water' from Algonquian by French Jesuits in the area. However scholars of the language translate it as 'place of strong current', which would certainly seem consistent.