| Unit Pref: | Imperial |
| Settlement Type: | Township |
| Official Name: | Prairie du Long Township |
| Image Map1: | Map of Illinois highlighting St. Clair County.svg |
| Mapsize1: | 150px |
| Map Caption1: | St. Clair County's location in Illinois |
| Subdivision Type: | Country |
| Subdivision Name: |  United States |
| Subdivision Type1: | State |
| Subdivision Type2: | County |
| Subdivision Name2: | St. Clair |
| Leader Title: | Supervisor |
| Established Title: | Established |
| Area Total Sq Mi: | 35.97 |
| Area Land Sq Mi: | 35.53 |
| Area Water Sq Mi: | 0.44 |
| Area Water Percent: | 1.22 |
| Population As Of: | 2010 |
| Population Density Sq Mi: | 63.2 |
| Utc Offset: | -6 |
| Timezone Dst: | CDT |
| Utc Offset Dst: | -5 |
| Coordinates: | 38.3519°N -89.9814°W |
| Elevation Ft: | 427 |
| Footnotes: | [1] |
| Pop Est As Of: | 2016 |
| Pop Est Footnotes: | [2] |
| Population Est: | 2200 |
| Blank Name: | FIPS code |
| Blank Info: | 17-163-61600 |
Prairie du Long Township is located in St. Clair County, Illinois. As of the 2010 census, its population was 2,244 and it contained 864 housing units.[3]
According to the 2010 census, the township has a total area of, of which (or 98.78%) is land and (or 1.22%) is water.[3]