| Abbreviation | Definition |
|---|---|
| INTO | Irish National Teachers' Organisation |
| IOI | Island of Ireland |
| IOPA | Irish Opinion Poll Archive |
| IP | Irish Potato |
| IPMN | Irish Posture and Mobility Network |
| IPN | Irish Pharmacy News |
| IPOI | Intellectual Property Office of Ireland |
| IPRT | Irish Penal Reform Trust |
| IPSC | Ireland Palestine Solidarity Campaign |
| IPSO | Irish Payment Services Organisation |
| IRC | Irish Research Council |
| IRDS | Irish Rally Driver Scheme |
| IREF | Irish Real Estate Funds |
| IRIU | Institutional Review of Irish Universities |
| IROC | Irish Redneck Out Cruising |
| IRWS | Irish Red and White Setter |
| ISAT | Irish Sleep Apnoea Trust |
| ISCL | Irish Society Of Comparative Law |
| ISDI | Irish Spatial Data Infrastructure |
| ISDL | Irish Self Determination League |