11 cities
| City | County | 2026 Pop. ↓ |
|---|---|---|
| Orchard Mesa | Mesa County | 6,542 |
| Orchard City | Delta County | 3,340 |
| Olathe | Montrose County | 1,950 |
| Ordway | Crowley County | 1,073 |
| Ouray | Ouray County | 919 |
| Oak Creek | Routt County | 839 |
| Otis | Washington County | 504 |
| Olney Springs | Crowley County | 287 |
| Ovid | Sedgwick County | 249 |
| Ophir | San Miguel County | 181 |
| Orchard | Morgan County | 107 |