| Official Name: | South Mount Vernon, Ohio |
| Settlement Type: | Census-designated place |
| Pushpin Map: | Ohio#USA |
| Pushpin Label: | South Mount Vernon |
| Coordinates: | 40.3811°N -82.4992°W |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Ohio |
| Subdivision Type2: | County |
| Subdivision Name2: | Knox |
| Subdivision Type3: | Township |
| Subdivision Name3: | Clinton |
| Area Footnotes: | [1] |
| Area Total Sq Mi: | 0.51 |
| Area Land Sq Mi: | 0.51 |
| Area Water Sq Mi: | 0.00 |
| Area Total Km2: | 1.31 |
| Area Land Km2: | 1.31 |
| Area Water Km2: | 0.00 |
| Population As Of: | 2020 |
| Population Total: | 714 |
| Population Density Km2: | 545.57 |
| Population Density Sq Mi: | 1413.86 |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Ft: | 1017 |
| Unit Pref: | Imperial |
| Postal Code Type: | ZIP Code |
| Postal Code: | 43050 (Mount Vernon) |
| Area Code: | 740/220 |
| Blank Name: | FIPS code |
| Blank Info: | 39-73530 |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 2806994 |
South Mount Vernon is a census-designated place (CDP) in Knox County, Ohio, United States, adjacent to the city of Mount Vernon. It was first listed as a CDP prior to the 2020 census.
The CDP is west of the center of Knox County, in Clinton Township. It is bordered to the north, east, and south by the city of Mount Vernon. It is bordered to the southeast by Dry Creek, a northeast-flowing tributary of the Kokosing River, part of the Walhonding River and subsequently Muskingum River watersheds leading to the Ohio River.
U.S. Route 36 (Harcourt Road) runs through the west side of the community, leading north and east into Mount Vernon, and southwest to Sunbury.