| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
| Opacac | city | Republika Crna Gora | Serbia & Montenegro | 42.2536111 | 19.0255556 | 1046 | 5133 |
| Opalanka | city | Republika Srbija | Serbia & Montenegro | 45.2508333 | 19.3919444 | 288 | 9951 |
| Opaljenik | city | Republika Crna Gora | Serbia & Montenegro | 43.3641667 | 19.3063889 | 2572 | 5108 |
| Opaljenik | city | Republika Srbija | Serbia & Montenegro | 43.5169444 | 20.1311111 | 2358 | 11554 |
| Opancarci | city | Republika Srbija | Serbia & Montenegro | 42.4233333 | 22.1425 | 3963 | 11758 |
| Opancine | city | Republika Srbija | Serbia & Montenegro | 43.2241667 | 19.6552778 | 2775 | 10257 |
| Opančarci | city | Republika Srbija | Serbia & Montenegro | 42.4233333 | 22.1425 | 3963 | 11758 |
| Opančine | city | Republika Srbija | Serbia & Montenegro | 43.2241667 | 19.6552778 | 2775 | 10257 |
| Oparic | city | Republika Srbija | Serbia & Montenegro | 43.7508333 | 21.1213889 | 1190 | 11506 |
| Oparić | city | Republika Srbija | Serbia & Montenegro | 43.7508333 | 21.1213889 | 1190 | 11506 |
| Opasanica | city | Republika Crna Gora | Serbia & Montenegro | 42.6805556 | 19.5413889 | 4114 | 5100 |
| Opasaonica | city | Republika Crna Gora | Serbia & Montenegro | 42.6805556 | 19.5413889 | 4114 | 5100 |
| Opatovo | city | Republika Crna Gora | Serbia & Montenegro | 42.4566667 | 18.6825 | 777 | 3126 |
| Opava | city | Republika Srbija | Serbia & Montenegro | 45.0522222 | 20.4302778 | 223 | 10618 |
| Opave | city | Republika Srbija | Serbia & Montenegro | 43.1233333 | 20.6491667 | 3648 | 13721 |
| Opazova | city | Republika Srbija | Serbia & Montenegro | 44.985 | 20.1608333 | 252 | 10087 |
| Opačac | city | Republika Crna Gora | Serbia & Montenegro | 42.2536111 | 19.0255556 | 1046 | 5133 |
| Opcine | city | Republika Crna Gora | Serbia & Montenegro | 43.0441667 | 19.1363889 | 4747 | 5069 |
| Opitra Stena | city | Republika Srbija | Serbia & Montenegro | 43.2038889 | 19.6911111 | 2614 | 9171 |
| Oplanic | city | Republika Srbija | Serbia & Montenegro | 43.9855556 | 20.6811111 | 892 | 11464 |
| Oplanici | city | Republika Srbija | Serbia & Montenegro | 43.7647222 | 20.6808333 | 892 | 11506 |
| Oplanić | city | Republika Srbija | Serbia & Montenegro | 43.9855556 | 20.6811111 | 892 | 11464 |
| Oplanići | city | Republika Srbija | Serbia & Montenegro | 43.7647222 | 20.6808333 | 892 | 11506 |
| Oplatnici | city | Republika Srbija | Serbia & Montenegro | 43.7647222 | 20.6808333 | 892 | 11506 |
| Oplatnići | city | Republika Srbija | Serbia & Montenegro | 43.7647222 | 20.6808333 | 892 | 11506 |
| Oporac | city | Republika Srbija | Serbia & Montenegro | 43.4225 | 20.2083333 | 3356 | 11571 |
| Opornica | city | Republika Srbija | Serbia & Montenegro | 44.05 | 20.8833333 | 564 | 11450 |
| Opovo | city | Republika Srbija | Serbia & Montenegro | 45.0522222 | 20.4302778 | 223 | 10618 |
| Oprashka | city | Republika Srbija | Serbia & Montenegro | 42.6919444 | 20.5416667 | 1561 | 19485 |
| Opraske | city | Republika Srbija | Serbia & Montenegro | 42.6919444 | 20.5416667 | 1561 | 19485 |
| Opraške | city | Republika Srbija | Serbia & Montenegro | 42.6919444 | 20.5416667 | 1561 | 19485 |
| Opterusa | city | Republika Srbija | Serbia & Montenegro | 42.3716667 | 20.7155556 | 1614 | 19587 |
| Opterusha | city | Republika Srbija | Serbia & Montenegro | 42.3716667 | 20.7155556 | 1614 | 19587 |
| Opteruša | city | Republika Srbija | Serbia & Montenegro | 42.3716667 | 20.7155556 | 1614 | 19587 |
| Optocici | city | Republika Crna Gora | Serbia & Montenegro | 42.2563889 | 18.9880556 | 708 | 5135 |
| Optočici | city | Republika Crna Gora | Serbia & Montenegro | 42.2563889 | 18.9880556 | 708 | 5135 |
| Opčine | city | Republika Crna Gora | Serbia & Montenegro | 43.0441667 | 19.1363889 | 4747 | 5069 |
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