| City | County | 2026 Pop. ↓ |
|---|---|---|
| Opelousas | St. Landry Parish | 14,962 |
| Oakdale | Allen Parish | 6,503 |
| Ossun | Lafayette Parish | 1,893 |
| Olla | LaSalle Parish | 1,332 |
| Oak Grove | West Carroll Parish | 1,331 |
| Oberlin | Allen Parish | 1,278 |
| Oil City | Caddo Parish | 868 |
| Oretta | Beauregard Parish | 599 |
| Oak Ridge | Morehouse Parish | 110 |