15 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Oak Ridge | Anderson County | 34,683 |
| Oakland | Fayette County | 11,199 |
| Oak Grove | Washington County | 4,421 |
| Oak Hill | Davidson County | 4,387 |
| Oneida | Scott County | 3,895 |
| Oliver Springs | Roane County | 3,464 |
| Olivet | Hardin County | 1,305 |
| Orebank | Sullivan County | 1,052 |
| Orlinda | Robertson County | 1,019 |
| Obion | Obion County | 961 |
| Ooltewah | Hamilton County | 406 |
| Ocoee | Polk County | 268 |
| Oakdale | Morgan County | 201 |
| Oak Grove | Macon County | 145 |
| Orme | Franklin County | 84 |