O
| Town and County | Population |
|---|---|
| O'Briensbridge-Montpelier, Clare and Limerick | 375 |
| Oilgate, Wexford | 265 |
| Oldcastle, Meath | 937 |
| Omeath, Louth | 231 |
| Oldtown, Fingal | 162 |
| Oola, Limerick | 391 |
| Oranmore, Galway | 1692 |
| Oughterard, Galway | 1209 |
Read more about this topic: List Of Towns In The Republic Of Ireland/2002 Census Records