| Official Name: | South Flannigan Township |
| Settlement Type: | Township |
| Unit Pref: | Imperial |
| Image Map1: | Map of Illinois highlighting Hamilton County.svg |
| Mapsize1: | 150px |
| Map Caption1: | Hamilton County's location in Illinois |
| Subdivision Type: | Country |
| Subdivision Type1: | State |
| Subdivision Type2: | County |
| Subdivision Name2: | Hamilton |
| Established Title: | Established |
| Established Date: | November 3, 1885 |
| Area Total Sq Mi: | 18.38 |
| Area Land Sq Mi: | 18.34 |
| Area Water Sq Mi: | 0.04 |
| Area Water Percent: | 0.21 |
| Population As Of: | 2020 |
| Population Total: | 148 |
| Population Density Sq Mi: | auto |
| Elevation M: | 162 |
| Elevation Ft: | 531 |
| Coordinates: | 37.9306°N -88.6556°W |
| Timezone: | CST |
| Utc Offset: | -6 |
| Timezone Dst: | CDT |
| Utc Offset Dst: | -5 |
| Postal Code Type: | ZIP codes |
| Postal Code: | 62817, 62890, 62935 |
| Blank Name: | FIPS code |
| Blank Info: | 17-065-70785 |
South Flannigan Township is one of twelve townships in Hamilton County, Illinois, USA. As of the 2020 census, its population was 148 and it contained 67 housing units.[1] It was formed from Flannigan Township.
According to the 2021 census gazetteer files, South Flannigan Township has a total area of 18.38sqmi, of which 18.34sqmi (or 99.79%) is land and 0.04sqmi (or 0.21%) is water.[2]
(This list is based on USGS data and may include former settlements.)
The township contains these two cemeteries: Good Hope and Winn.
As of the 2020 census[3] there were 148 people, 7 households, and 7 families residing in the township. The population density was 8.05PD/sqmi. There were 67 housing units at an average density of 3.65/sqmi. The racial makeup of the township was 94.59% White, 0.00% African American, 0.00% Native American, 0.00% Asian, 0.00% Pacific Islander, 0.00% from other races, and 5.41% from two or more races. Hispanic or Latino of any race were 0.68% of the population.
There were 7 households, all of which had children under the age of 18 living with them, and all were married couples living together. The average household size was 3.29 and the average family size was 3.29.
The township's age distribution consisted of 43.5% under the age of 18, 0.0% from 18 to 24, 56.5% from 25 to 44, 0% from 45 to 64, and 0.0% who were 65 years of age or older. The median age was 32.2 years. For every 100 females, there were 283.3 males. For every 100 females age 18 and over, there were 116.7 males.