| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
|---|
| Obrero | city | Puerto Rico | United States | 18.47472 | -66.7425 | 36 | 23980 |
| Obrero | city | Puerto Rico | United States | 18.43611 | -66.05278 | 6 | 264480 |
| Ocean Park | city | Puerto Rico | United States | 18.45417 | -66.05472 | 0 | 264480 |
| Oceanview | city | Puerto Rico | United States | 18.47222 | -66.73639 | 6 | 23980 |
| Ojo de Agua | city | Puerto Rico | United States | 18.45083 | -66.39972 | 65 | 62370 |
| Olimpo | city | Puerto Rico | United States | 18.00389 | -66.10861 | 285 | 41545 |
| Olivares | city | Puerto Rico | United States | 18.00417 | -67.07111 | 104 | 24184 |
| Ollas Hondas | city | Puerto Rico | United States | 18.04889 | -66.52944 | 157 | 54625 |
| Oriente | city | Puerto Rico | United States | 18.44333 | -66.71472 | 19 | 38444 |
| Orocovis | city | Puerto Rico | United States | 18.22889 | -66.39139 | 2017 | 27456 |
| Ortiga | city | Puerto Rico | United States | 18.16778 | -66.44778 | 1988 | 24138 |
| Ortiz | city | Puerto Rico | United States | 18.32861 | -66.32028 | 695 | 54782 |
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