| Official Name: | South Ilion, New York |
| Settlement Type: | Census-designated place |
| Pushpin Map: | New York#USA |
| Pushpin Label: | South Ilion |
| Pushpin Label Position: | bottom |
| Coordinates: | 42.995°N -75.0486°W |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | New York |
| Subdivision Type2: | County |
| Subdivision Name2: | Herkimer |
| Subdivision Type3: | Town |
| Subdivision Name3: | German Flatts |
| Area Footnotes: | [1] |
| Area Total Sq Mi: | 0.44 |
| Area Land Sq Mi: | 0.44 |
| Area Water Sq Mi: | 0.00 |
| Area Total Km2: | 1.15 |
| Area Land Km2: | 1.14 |
| Area Water Km2: | 0.01 |
| Population As Of: | 2020 |
| Population Density Km2: | 104.59 |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Ft: | 560 |
| Postal Code Type: | ZIP Code |
| Postal Code: | 13357 (Ilion) |
| Area Code: | 315/680 |
| Blank Name: | FIPS code |
| Blank Info: | 36-69265 |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 2806942 |
| Population Total: | 119 |
| Unit Pref: | Imperial |
| Population Density Sq Mi: | 271.07 |
South Ilion is a hamlet and census-designated place (CDP) in the town of German Flatts in Herkimer County, New York, United States. It was first listed as a CDP prior to the 2020 census.
The community is in southwestern Herkimer County, in the southwestern part of German Flatts. The hamlet is in a narrow valley that leads upstream into Spinnerville Gulf and is south of the village of Ilion. New York State Route 51 runs through the northwestern side of the CDP, following the valley of Steele Creek. The highway leads north into Ilion and southwest 10miles to East Winfield.