- O’Brien’s Bridge
- O’Briensbridge
- O'Callagha Park
- O’Callaghansmills
- O’Connell Bridge
- Oaghley
- Oakhampton
- Oaklands
- Oatfield
- Odell Ville
- Oghermong
- Ogonnelloe
- Oil Mill Bridge
- Old Bride Bridge
- Old Bridge
- Old Chapel Cross Roads
- Old Courth
- Old Kildimo
- Old Pike Bridge
- Old Port House
- Old Twopothouse Cross Roads
- Oldcastletown
- Oldchapel
- Oldcourt
- Oldgrange
- Oldmill Bridge
- Oldtown
- Oldtown
- Oola
- Oolagh Bridge