| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
|---|
| Oakdale | city | Connecticut | United States | 41.46611 | -72.15778 | 285 | 18778 |
| Oakdale Manor | city | Connecticut | United States | 41.44444 | -73.25278 | 200 | 15644 |
| Oakland | city | Connecticut | United States | 41.80611 | -72.51833 | 200 | 69318 |
| Oakland Gardens | city | Connecticut | United States | 41.7425 | -72.78667 | 298 | 114663 |
| Oakland Gardens | city | Connecticut | United States | 41.7325 | -72.78417 | 298 | 114663 |
| Oakville | city | Connecticut | United States | 41.59333 | -73.08583 | 396 | 44071 |
| Obtuse Hill | city | Connecticut | United States | 41.46639 | -73.36194 | 498 | 15418 |
| Occum | city | Connecticut | United States | 41.595 | -72.05111 | 65 | 18825 |
| Old Avon Village | city | Connecticut | United States | 41.8075 | -72.82944 | 187 | 28484 |
| Old Greenwich | city | Connecticut | United States | 41.02278 | -73.56528 | 49 | 82878 |
| Old Lyme | city | Connecticut | United States | 41.31583 | -72.32944 | 45 | 10227 |
| Old Lyme Shores | city | Connecticut | United States | 41.29028 | -72.27528 | 29 | 5389 |
| Old Mystic | city | Connecticut | United States | 41.39139 | -71.96222 | 134 | 17888 |
| Old Saybrook | city | Connecticut | United States | 41.29167 | -72.37667 | 22 | 16488 |
| Oneco | city | Connecticut | United States | 41.69361 | -71.80889 | 367 | 5378 |
| Orange | city | Connecticut | United States | 41.27833 | -73.02611 | 200 | 77836 |
| Orcutts | city | Connecticut | United States | 41.97667 | -72.32222 | 570 | 10123 |
| Ore Hill | city | Connecticut | United States | 41.95722 | -73.4675 | 800 | 2764 |
| Oronoke | city | Connecticut | United States | 41.54139 | -73.08972 | 498 | 50317 |
| Oronoque | city | Connecticut | United States | 41.24778 | -73.10194 | 3 | 84116 |
| Oronoque Hills North | city | Connecticut | United States | 41.25389 | -73.11333 | 203 | 61950 |
| Oronoque Hills South | city | Connecticut | United States | 41.24722 | -73.11167 | 141 | 84116 |
| Osprey Beach | city | Connecticut | United States | 41.31556 | -72.09417 | 0 | 44249 |
| Oswegatchie | city | Connecticut | United States | 41.355 | -72.17667 | 68 | 20488 |
| Otter Cove Estates | city | Connecticut | United States | 41.33722 | -72.37111 | 98 | 10798 |
| Overlook | city | Connecticut | United States | 41.56667 | -73.04861 | 429 | 109944 |
| Owenoke | city | Connecticut | United States | 41.10667 | -73.36083 | 0 | 41019 |
| Ox Hill | city | Connecticut | United States | 41.22833 | -73.21944 | 196 | 133100 |
| Oxford | city | Connecticut | United States | 41.43389 | -73.11722 | 383 | 23177 |
| Oxford Park | city | Connecticut | United States | 41.60806 | -72.67028 | 147 | 52695 |
| Oxford Village | city | Connecticut | United States | 41.76611 | -72.56333 | 157 | 82398 |
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