| Oblong Township, IL (Township) |
| Obrien, MN (Township) |
| Obrien, TX (City) |
| Ocala , FL (City) |
| Occoquan, VA (Town) |
| Ocean Beach, NY (Village) |
| Ocean Breeze, FL (Town) |
| Ocean City, NJ (City) |
| Ocean City, MD (Town) |
| Ocean County, NJ (County) |
| Ocean Gate, NJ (Borough) |
| Ocean Isle Beach, NC (Town) |
| Ocean Ridge , FL (Town) |
| Ocean Shores, WA (City) |
| Ocean Springs, MS (City) |
