- Oakwood
- Oakwood
- Oakwood
- Oakwood Knolls
- Oakwood Manor
- Oakwood Overlook
- Oakwood Park
- Oakwood Village
- Obretch Estates
- Ocean
- Oceola Estates
- Octararo Lakes
- Octoraro
- Octoraro Park
- Oddessy
- Odenton Heights
- Odenton Park
- Odyssey
- Oella
- Offutt Island
- Offutt Ridge
- Oil City
- Oklahoma
- Olacin
- Old Annapolis Neck
- Old Baltimore
- Old Bayside
- Old Cedar Point
- Old Colony Cove
- Old County Estates