| Code | Name | Region |
|---|---|---|
| IECTL | Cratloe | CE |
| IECGW | Craughwell | G |
| IECRO | Crookhaven | |
| IECKS | Crookstown | |
| IECDY | Crossdoney | CN |
| IECSG | Crosserlough | CN |
| IECUR | Curracloe | WX |
| IECUH | Curragh | KE |
| IEDAL | Dalkey | D |
| IEDEA | Deans Grange | D |
| IEDEL | Delgany | WW |
| IEDYB | Derrybeg | DL |
| IEDER | Derryveagh | |
| IEDIN | Dingle | |
| IEDAT | Donabate | D |
| IECHD | Cloghjordan | TA |
| IECLO | Cloghore | |
| IECLR | Cloghran | |
| IECKY | Clonakilty | CO |
| IECSL | Clonaslee | LS |
| IECFY | Clonbulloge | OY |
| IECLK | Clondalkin | |
| IECLE | Clonee | |
| IECLS | Clones | |
| IECLL | Clonmel | |
| IECHU | Clonshaugh | D |
| IECTT | Clontibret | |
| IECLN | Cloonlara | CE |
| IECCT | Coastal Control Terminal | |
| IECOB | Cobh | |
| IECOL | Collinstown | |
| IECON | Collon | LH |
| IECLY | Collooney | |
| IECOA | Coolea | CO |
| IEFGY | Coolock | D |
| IECAD | Castleisland | KY |
| IECLM | Castlemahon | LK |
| IECMA | Castlemaine | KY |
| IETLK | Castlenock | CW |
| IECPD | Castlepollard | WH |
| IECAA | Castlerea | |
| IECTN | Castletown | LS |
| IECTB | Castletown Bearhaven | CO |
| IECAU | Causeway | |
| IECAV | Cavan | |
| IECEL | Celbridge | |
| IECHT | Charlestown | MO |
| IECHA | Charleville | CO |
| IECTW | Churchtown | CO |
| IECNE | Clane | KE |