7 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Orangeburg | Orangeburg County | 13,428 |
| Oak Grove | Lexington County | 11,658 |
| Olympia | Richland County | 1,533 |
| Oakland | Lee County | 889 |
| Olanta | Florence County | 549 |
| Oswego | Lee County | 440 |
| Olar | Bamberg County | 204 |