9 cities
| City | Parish | 2026 Pop. ↓ |
|---|---|---|
| Opelousas | St. Landry Parish | 14,878 |
| Oakdale | Allen Parish | 6,400 |
| Ossun | Lafayette Parish | 1,893 |
| Oak Grove | West Carroll Parish | 1,308 |
| Olla | LaSalle Parish | 1,292 |
| Oberlin | Allen Parish | 1,267 |
| Oil City | Caddo Parish | 852 |
| Oretta | Beauregard Parish | 599 |
| Oak Ridge | Morehouse Parish | 106 |