| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
|---|
| O'Briens Corner | city | Massachusetts | United States | 42.0875 | -72.64028 | 144 | 84572 |
| Oak Bluffs | city | Massachusetts | United States | 41.45417 | -70.5625 | 3 | 5996 |
| Oak Grove | city | Massachusetts | United States | 42.43472 | -71.075 | 45 | 294484 |
| Oak Grove Village | city | Massachusetts | United States | 41.7025 | -71.12639 | 134 | 105312 |
| Oak Hill | city | Massachusetts | United States | 42.25833 | -71.79028 | 547 | 146453 |
| Oak Hill Park | city | Massachusetts | United States | 42.29444 | -71.18611 | 98 | 219275 |
| Oak Island | city | Massachusetts | United States | 42.425 | -70.9875 | 0 | 169322 |
| Oakdale | city | Massachusetts | United States | 42.20417 | -72.625 | 223 | 109850 |
| Oakdale | city | Massachusetts | United States | 42.39028 | -71.79389 | 423 | 14502 |
| Oakdale | city | Massachusetts | United States | 42.24028 | -71.15278 | 78 | 131974 |
| Oakdale | city | Massachusetts | United States | 41.75833 | -70.70833 | 9 | 15780 |
| Oakham | city | Massachusetts | United States | 42.35278 | -72.04583 | 892 | 4795 |
| Oakland | city | Massachusetts | United States | 41.91111 | -71.13889 | 49 | 37054 |
| Oakland Heights | city | Massachusetts | United States | 42.225 | -71.78056 | 488 | 114838 |
| Oakland Square | city | Massachusetts | United States | 42.03611 | -70.80056 | 98 | 23261 |
| Oakland Vale | city | Massachusetts | United States | 42.47167 | -71.03194 | 72 | 157918 |
| Oaklands | city | Massachusetts | United States | 42.63333 | -71.28611 | 147 | 109666 |
| Ocean Bluff | city | Massachusetts | United States | 42.09722 | -70.65417 | 36 | 13319 |
| Ocean Grove | city | Massachusetts | United States | 41.72917 | -71.20972 | 13 | 48839 |
| Ocean Heights | city | Massachusetts | United States | 41.40639 | -70.55222 | 3 | 5332 |
| Ocean View | city | Massachusetts | United States | 42.68472 | -70.625 | 3 | 8783 |
| Oklahoma Heights | city | Massachusetts | United States | 41.43889 | -70.60917 | 49 | 7540 |
| Old Boat Point | city | Massachusetts | United States | 42.23833 | -70.97333 | 3 | 136245 |
| Old Cambridge | city | Massachusetts | United States | 42.37778 | -71.11667 | 36 | 498198 |
| Old City | city | Massachusetts | United States | 42.6375 | -71.73 | 449 | 13990 |
| Old Common | city | Massachusetts | United States | 42.18472 | -71.78611 | 577 | 46246 |
| Old Harbor | city | Massachusetts | United States | 41.6 | -69.98333 | 0 | 967 |
| Old Hill | city | Massachusetts | United States | 42.10417 | -72.56806 | 196 | 169241 |
| Old Mouth North River | city | Massachusetts | United States | 42.12583 | -70.67972 | 3 | 16470 |
| Old North Ashburnham Station | city | Massachusetts | United States | 42.65556 | -71.98333 | 1056 | 10656 |
| Old Oaken Bucket Homestead | city | Massachusetts | United States | 42.17778 | -70.75639 | 45 | 27326 |
| Old Quaker Meetinghouse | city | Massachusetts | United States | 41.74639 | -70.45889 | 9 | 15598 |
| Old Silver Beach | city | Massachusetts | United States | 41.62667 | -70.63667 | 29 | 9233 |
| Old Spain | city | Massachusetts | United States | 42.24333 | -70.94417 | 45 | 99807 |
| Old Sturbridge Village | city | Massachusetts | United States | 42.10694 | -72.09917 | 597 | 10595 |
| Old Town Landing | city | Massachusetts | United States | 41.80417 | -71.12139 | 3 | 19555 |
| Olde English Village | city | Massachusetts | United States | 42.55833 | -71.99833 | 994 | 21608 |
| Oldham Pines | city | Massachusetts | United States | 42.07222 | -70.82917 | 82 | 27893 |
| Oldham Village | city | Massachusetts | United States | 42.06667 | -70.82917 | 78 | 27893 |
| Onset | city | Massachusetts | United States | 41.74167 | -70.65833 | 0 | 17182 |
| Onset Station | city | Massachusetts | United States | 41.75611 | -70.6775 | 9 | 15780 |
| Orange | city | Massachusetts | United States | 42.59028 | -72.31028 | 593 | 7206 |
| Orchard Hills Estates | city | Massachusetts | United States | 42.10722 | -71.83722 | 646 | 24649 |
| Orient Heights | city | Massachusetts | United States | 42.3875 | -71.00417 | 3 | 267865 |
| Orleans | city | Massachusetts | United States | 41.78972 | -69.99028 | 29 | 11679 |
| Osterville | city | Massachusetts | United States | 41.62833 | -70.3875 | 19 | 21927 |
| Otis | city | Massachusetts | United States | 42.19306 | -73.09222 | 1233 | 1277 |
| Otis Wood Lanes | city | Massachusetts | United States | 42.18556 | -73.10139 | 1499 | 1277 |
| Otter River | city | Massachusetts | United States | 42.59778 | -72.05139 | 905 | 13248 |
| Overbrook | city | Massachusetts | United States | 42.305 | -71.325 | 147 | 68610 |
| Owen District | city | Massachusetts | United States | 42.15917 | -72.69056 | 396 | 42149 |
| Oxford | city | Massachusetts | United States | 42.11667 | -71.86528 | 498 | 24649 |
| Oxford | city | Massachusetts | United States | 41.65556 | -70.90694 | 49 | 96980 |
| Oxford Heights | city | Massachusetts | United States | 42.17361 | -71.87917 | 649 | 21600 |
| Oyster Harbors | city | Massachusetts | United States | 41.62083 | -70.41583 | 9 | 10764 |
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