Barrios de Ohio O
- Oakley (28)
- Ohio City (17)
- Old Brooklyn (22)
- Old Dayton (1)
- Old North Columbus (55)
- Old North Dayton (5)
- Old West End (6)
- Olde Orchard (2)
- Olde Sawmill (6)
- Olde Town East (33)
- Olde Town East-Columbus (22)
- Olde Towne (6)
- Olentangy (6)
- Olentangy Commons (2)
- Olentangy High Bluffs (2)
- ONYX (4)
- Oregon (5)
- Oriole Heights (1)
- Ottawa (29)
- Ottawa Hills (1)
- Outer Campbell/Struthers (3)
- Outer Canfield/Poland (4)
- Outer Canton (42)
- Outer Centerville/Kettering (42)
- Outer Dublin/Hilliard (28)
- Outer East Dayton (11)
- Outer East/Tallmadge (5)
- Outer Greater Hilltop (30)
- Outer Northeast (13)
- Outer Northeast Columbus (8)
- Outer Southern Columbus (20)
- Outer Upper Arlington (15)
- Over-The Rhine (18)