Locations
- O'Brien's Place
- O'Connell Avenue
- O'Connell Bridge
- O'Connell Street
- Oadby
- Oak Terrace
- Oaklands Park
- Oakley Grange
- Oakley House
- Oakley Road
- Oakstown
- Oberstown
- Old Cabra Road
- Old Cavehill Road
- Old Kent Road
- Old Street
- Oldcastle
- Oldham Place
- Oldtown Upper
- Omagh
- Oranmore
- Orchard Road
- Ordnance Road
- Oriel Grove Avenue
- Oriel Street
- Oriel Street Lower
- Oriel Street Upper
- Ormond Quay
- Ormond Quay Lower
- Ormond Quay Upper
- Ormond Road
- Orwell Park
- Orwell Road
- Osborne Lodge
- Osborne Road
- Ossory Road
- Ovoca Road
- Oxford Road
- Oxford Street
- Oxfordshire
- Oxmantown Road