| Unit Pref: | Imperial |
| Settlement Type: | Township |
| Official Name: | Mercer Township |
| Image Map1: | Map of Illinois highlighting Mercer County.svg |
| Mapsize1: | 150px |
| Map Caption1: | Mercer County's location in Illinois |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Illinois |
| Subdivision Type2: | County |
| Subdivision Name2: | Mercer |
| Leader Title: | Supervisor |
| Established Title: | Established |
| Established Date: | November 8, 1853 |
| Area Total Sq Mi: | 35.47 |
| Area Land Sq Mi: | 35.42 |
| Area Water Sq Mi: | 0.05 |
| Area Water Percent: | 0.14 |
| Population As Of: | 2010 |
| Population Density Sq Mi: | 114.9 |
| Utc Offset: | -6 |
| Timezone Dst: | CDT |
| Utc Offset Dst: | -5 |
| Pop Est As Of: | 2016 |
| Pop Est Footnotes: | [1] |
| Population Est: | 3923 |
| Blank Name: | FIPS code |
| Blank Info: | 17-131-48398 |
Mercer Township is located in Mercer County, Illinois. As of the 2010 census, its population was 4,071 and it contained 1,873 housing units.[2] Mercer Township changed its name from Centre Township on an unknown date sometime before 1921. Mercer Township contains Aledo, the county seat of Mercer County.
According to the 2010 census, the township has a total area of, of which (or 99.86%) is land and (or 0.14%) is water.[2]