10 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Owensboro | Daviess County | 60,052 |
| Oakbrook | Boone County | 10,297 |
| Oak Grove | Christian County | 7,996 |
| Owenton | Owen County | 1,657 |
| Orchard Grass Hills | Jefferson County | 1,625 |
| Owingsville | Bath County | 1,600 |
| Olive Hill | Carter County | 1,522 |
| Old Brownsboro Place | Jefferson County | 368 |
| Oneida | Clay County | 234 |
| Oakland | Warren County | 189 |