| City | 2026 Pop. ↓ |
|---|---|
| Omsk | 1,098,258 |
| Orenburg | 536,168 |
| Orel | 286,629 |
| Odintsovo | 192,326 |
| Orsk | 183,232 |
| Obninsk | 133,455 |
| Oktyabrsky | 116,593 |
| Orekhovo-Zuevo | 104,896 |
| Ozersk | 74,556 |
| Otradnyy | 45,769 |
| Osinniki | 38,263 |
| Ob | 31,443 |
| Ozery | 24,079 |
| Ostrov | 20,538 |
| Olenegorsk | 20,525 |
| Oktyabrsk | 19,213 |
| Osa | 18,915 |
| Omutninsk | 18,663 |
| Onega | 15,352 |
| Ocher | 14,080 |
| Oboyan | 11,278 |
| Opochka | 9,101 |
| Okulovka | 8,893 |
| Olekminsk | 8,397 |
| Obluche | 7,623 |
| Olonets | 7,408 |
| Okhansk | 6,114 |
| Orlov | 5,249 |
| Ozersk | 4,263 |
| Ostrovnoy | 1,165 |