| Families |
Ethnic Group |
Branch of |
| Cavan |
|
O'Keevan |
| Cawley |
|
MacAwley (Fermanagh) |
| Chalmers |
|
Cameron |
| Cheyne, Chesney |
IVL - Ulster |
|
| Cheyne |
IVL - Northern Scotland |
|
| Chisholm |
Normans |
|
| Clarke |
|
O'Cleary |
| Clarke |
|
O'Hara |
| Clarke |
IVL |
|
| Cleary |
|
O'Hara |
| Coffey |
IVL - Connacht, Kerry, Tipperary |
|
| Cogley |
|
O'Quigley |
| Collier, Colyear |
|
Robertson |
| Collier, Colyer |
IVL - Ireland |
|
| Collins |
|
O'Cullane |
| Collins |
IVL - Ireland |
|
| Colquhoun |
Normans |
|
| Colson |
|
MacDonald (Clan Donald) |
| Comrie |
|
MacGregor |
| Condon |
IVL |
|
| Condon |
Normans |
|
| Conlon, Connellan |
|
O'Quinlan |
| Conlon, Connellan |
IVL - North Connacht |
|
| Conn |
|
MacDonald (Clan Donald) |
| Conn |
IVL - South Scotland |
|
| Conry |
|
O'Mulconry |
| Conry |
IVL - Galway |
|
| Cowan |
|
MacKeown |
| Cowan |
IVL - Ireland, S. Scotland |
|
| Cowhey |
IVL - Connacht |
|
| Cowhey, Cowhig |
|
O'Coffey |
| Creagh |
Erainn |
|
| Creagh |
IVL - Munster |
|
| Crean, Crehan, Creghan |
IVL - Leinster, Galway, South Ireland |
|
| Creghan, Crehan |
|
O'Crean |
| Crehan |
IVL - Ulster |
|
| Crerar |
|
MacKintosh |
| Cullen |
|
MacQuillan |
| Cullen |
|
O'Cullane |
| Cullen |
Gaels |
O'Cullinan |
| Cullen |
IVL - Ireland, South Scotland |
|
| Cumming |
IVL - Ireland |
|
| Cumming, Comyn, Cummin |
Normans |
|
| Cunnagher |
|
Joyce |
|
