Barrios de Maryland O
- Oakenshawe (8)
- Oakland Mills (4)
- Oaklee (1)
- Oakview (1)
- Odenton (19)
- Old Farm (2)
- Old Town Hyattsville (22)
- Oldtown (3)
- Oliver (7)
- Olney (5)
- Original Northwood (1)
- Otterbein (4)
- Outer Downtown/Maugansville (39)
- Outer Robinwood/Paramnt/Fountain Head (11)
- Overlea (7)
- Overlook (2)
- Owen Brown (9)
- Owings Mills (32)
- Oxon Hill (3)