| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
|---|
| Obalysh | city | Respublika Mariy-El | Russia | 57.0833333 | 48.8666667 | 610 | 1689 |
| Obdasola | city | Respublika Mariy-El | Russia | 57.0188889 | 49.0830556 | 554 | 2559 |
| Obdor-Sola | city | Respublika Mariy-El | Russia | 56.4 | 48.8166667 | 501 | 1391 |
| Oktyabr'skiy | city | Respublika Mariy-El | Russia | 56.3113889 | 48.6063889 | 423 | 1415 |
| Ol'kiniyev | city | Respublika Mariy-El | Russia | 56.8833333 | 49.55 | 567 | 1780 |
| Olory | city | Respublika Mariy-El | Russia | 56.7422222 | 49.5580556 | 465 | 2353 |
| Onakaner | city | Respublika Mariy-El | Russia | 57 | 48.8833333 | 505 | 1889 |
| Onuchino | city | Respublika Mariy-El | Russia | 56.7666667 | 49.3166667 | 521 | 2130 |
| Or'yer | city | Respublika Mariy-El | Russia | 56.4366667 | 48.3152778 | 439 | 1652 |
| Or-Ishit | city | Respublika Mariy-El | Russia | 56.75 | 48.7833333 | 587 | 1920 |
| Orekhov Yar | city | Respublika Mariy-El | Russia | 56.25 | 46.8166667 | 209 | 737 |
| Orishut' | city | Respublika Mariy-El | Russia | 56.75 | 48.7833333 | 587 | 1920 |
| Orlovskiy | city | Respublika Mariy-El | Russia | 56.9 | 48.15 | 403 | 1470 |
| Orsha | city | Respublika Mariy-El | Russia | 56.9094444 | 48.5108333 | 620 | 1853 |
| Orshanka | city | Respublika Mariy-El | Russia | 56.9141667 | 47.8955556 | 334 | 1478 |
| Orsyuba | city | Respublika Mariy-El | Russia | 57.0391667 | 49.6172222 | 462 | 1220 |
| Oshetskiy | city | Respublika Mariy-El | Russia | 56.9666667 | 49.4166667 | 587 | 2378 |
| Oshkaner | city | Respublika Mariy-El | Russia | 57 | 48.8833333 | 505 | 1889 |
| Oshlan | city | Respublika Mariy-El | Russia | 56.85 | 49.8 | 488 | 1553 |
| Oshurga | city | Respublika Mariy-El | Russia | 56.65 | 47.75 | 410 | 1642 |
| Oshut"yaly | city | Respublika Mariy-El | Russia | 56.1891667 | 48.4191667 | 242 | 1573 |
| Oshut'yal | city | Respublika Mariy-El | Russia | 56.1891667 | 48.4191667 | 242 | 1573 |
| Osipsola | city | Respublika Mariy-El | Russia | 56.4172222 | 48.7338889 | 485 | 1390 |
| Otar | city | Respublika Mariy-El | Russia | 56.9761111 | 48.3072222 | 416 | 1535 |
| Otary | city | Respublika Mariy-El | Russia | 56.3333333 | 46.85 | 324 | 375 |
| Otary | city | Respublika Mariy-El | Russia | 56.9761111 | 48.3072222 | 416 | 1535 |
| Otumbal | city | Respublika Mariy-El | Russia | 56 | 48.6666667 | 564 | 3135 |
| Ozerki | city | Respublika Mariy-El | Russia | 56.3808333 | 46.5286111 | 249 | 1359 |
| Ozerki | city | Respublika Mariy-El | Russia | 56.1716667 | 48.3644444 | 314 | 1497 |
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