| Oak Grove, Dunfanaghy | — | 15 |
| Oakfield Crescent, Buncrana | — | 5 |
| Oakland Heights, Drumkeen | — | 5 |
| Oaklands Park, Gortlee | — | 5 |
| Oaklands Park, Letterkenny | €249,500 | 11 |
| Oakwood Park, Lismonaghan | — | 5 |
| Old Road, Mountcharles | €345,000 | 10 |
| Oliver Plunkett House, Oliver Plunkett Rd | — | 8 |
| Oran Hill, Letterkenny | — | 6 |
| Orchard Crescent, High Rd | €127,500 | 6 |
| Orchard Dr, Donegal Town | €212,500 | 11 |
| Orchard Grove, Ballyraine | — | 5 |
| Orchard Grove, Letterkenny | — | 7 |
| Orchard Grove, Newtowncunningham | — | 9 |
| Orchard Park, Donegal Town | — | 7 |
| Oughtmeen, Dungloe | — | 5 |
| Owenteskna, Glencolmcille | — | 6 |