O
- (County Cork) Old Courth
- (Kerry) Ownagarry Bridge
- (Kerry) O’Connell Bridge
- (County Cork) Oldcourt
- (County Cork) Old Port House
- (County Cork) Old Chapel Cross Roads
- (County Cork) Owen’s Island
- (Kerry) Ormond’s Island
- (Kerry) Oghermong
- (Kerry) Oughtiv
- (Kerry) Owroe Bridge
- (Limerick City and County Council) Oola
- (Clare) O’Briensbridge
- (Limerick City and County Council) Old Kildimo