| City | County | 2026 Pop. ↓ |
|---|---|---|
| Owensboro | Daviess County | 60,968 |
| Oakbrook | Boone County | 9,557 |
| Oak Grove | Christian County | 7,844 |
| Owenton | Owen County | 1,688 |
| Orchard Grass Hills | Jefferson County | 1,642 |
| Owingsville | Bath County | 1,612 |
| Olive Hill | Carter County | 1,526 |
| Old Brownsboro Place | Jefferson County | 384 |
| Oakland | Warren County | 192 |
| Onton | Webster County | 107 |
| Oneida | Clay County | 100 |