| Name | Position | Party | Constituency |
|---|---|---|---|
| Eoin Ó Broin | TD | Sinn Féin | Dublin Mid-West |
| Eoin Ó Broin | Councillor | Independent | Clondalkin |
| Seán Ó Buachalla | Former Representative | Green Party | |
| Diarmaid O Cadhla | Former Representative | Independent | |
| Diarmaid Ó Cadhla | Former Representative | Independent | |
| Caoimhghín Ó Caoláin | Former Representative | Sinn Féin | |
| Marc Ó Cathasaigh | Councillor | Green Party | Tramore-Waterford City West |
| Séighin Ó Ceallaigh | Former Representative | Sinn Féin | |
| Eoghan Ó Ceannabháin | Former Representative | People Before Profit | |
| Naoise Ó Cearúil | Councillor | Fianna Fáil | Maynooth |
| Pádraig Ó Céidigh | Former Representative | Independent | |
| Trevor Ó Clochartaigh | Former Representative | Unknown | |
| Proinsias Ó Conaráin | Former Representative | Aontú | |
| Cathal Ó Conchúir | Former Representative | Sinn Féin | |
| Cormac Ó Corcoráin | Former Representative | Aontú | |
| Dáithí Ó Cualáin | Councillor | Unknown | Conamara South |
| Seosamh Ó Cualúin | Former Representative | Independent | |
| Éamon Ó Cuív | TD | Fianna Fáil | Galway West |
| Tomás Ó Curraoin | Councillor | Independent | Conamara South |
| Brian Ó Domhnaill | Former Representative | Fianna Fáil | |
| Seamus Ó Domhnaill | Former Representative | Fianna Fáil | |
| Niall Ó Donnghaile | Former Representative | Sinn Féin | |
| Daithí Ó Fallamháin | Former Representative | Irish Freedom Party | |
| Séafra Ó Faoláin | Councillor | Green Party | Blackrock |
| Sean Ó Fearghail | Ceann Comhairle | Fianna Fáil | Kildare South |
| John Shéamuis Ó Fearraig | Councillor | Sinn Féin | Glenties |
| Oisín Ó Halmhain | Former Representative | Green Party | |
| Donnchadh Ó Laoghaire | TD | Sinn Féin | Cork South-Central |
| Con Óg Ó Laoghaire | Former Representative | Irish Freedom Party | |
| Aengus Ó Maoláin | Former Representative | Social Democrats |