| City | County | 2026 Pop. ↓ |
|---|---|---|
| Orchard Mesa | Mesa County | 6,542 |
| Orchard City | Delta County | 3,331 |
| Olathe | Montrose County | 1,914 |
| Ordway | Crowley County | 1,058 |
| Ouray | Ouray County | 931 |
| Oak Creek | Routt County | 827 |
| Otis | Washington County | 499 |
| Olney Springs | Crowley County | 285 |
| Ovid | Sedgwick County | 253 |
| Ophir | San Miguel County | 182 |
| Orchard | Morgan County | 107 |