| City | County | 2026 Pop. ↓ |
|---|---|---|
| Oak Ridge | Anderson County | 36,223 |
| Oakland | Fayette County | 11,264 |
| Oak Grove | Washington County | 4,496 |
| Oak Hill | Davidson County | 4,496 |
| Oneida | Scott County | 3,923 |
| Oliver Springs | Roane County | 3,462 |
| Olivet | Hardin County | 1,669 |
| Orlinda | Robertson County | 1,044 |
| Orebank | Sullivan County | 956 |
| Obion | Obion County | 951 |
| Ooltewah | Hamilton County | 443 |
| Ocoee | Polk County | 258 |
| Oak Grove | Macon County | 213 |
| Oakdale | Morgan County | 203 |
| Orme | Franklin County | 84 |