| Novi Financial, Inc. | Dublin City Council |
| Novus Diagnostics Ltd | |
| NTR plc | |
| Nua Surgical | |
| NUACOM | |
| Nualtra | |
| Nuasoft Web Services | Dublin City Council |
| Nuhouse Design | |
| Nultan | |
| Numra | |
| Nuritas | Dublin City Council |
| Nutritics | |
| Nutshell Creative Communication | Cork City Council |
| Nvolve | |
| O.C.E. Technology Ltd | |
| Obit | Limerick City and County Council |
| Oblivious Software Ltd | |
| Ocuco Ltd | Fingal County Council |
| Office Suites | |
| Offr.io | |
| OGX Marketing | |
| OkJob | |
| Olas.ie | Dún Laoghaire-Rathdown County Council |
| OmniSpirant Therapeutics | |
| Onaware | Waterford City and County Council |
| OncoAssure Ltd | |
| OnePageCRM | Galway City Council |
| OnePosting | Dublin City Council |
| Oneview Healthcare | |
| ONK Therapeutics Ltd | |
| Online365.ie | Dublin City Council |
| ONS Ltd | Clare County Council |
| OnSight Designs Ltd | Limerick City and County Council |
| OnTheWeb | Galway City Council |
| OPCWare | Cork City Council |
| Openet | Dublin City Council |
| OpenMind | Dublin City Council |
| OpenPoint | Limerick City and County Council |
| OpenSky | |
| OpinionX Ltd | |
| Oracle Ireland | Dublin City Council |
| Orbigo Solutions Ltd | Dublin City Council |
| Orbit Technologies Dublin | |
| Orbsen Therapeutics | |
| Origin Enterprises plc | |
| Origina | Dún Laoghaire-Rathdown County Council |
| Orlin Technology Ltd | Fingal County Council |
| Ornua Co-operative Ltd | |
| OSD Digital Agency | Sligo County Council |
| Ostoform Ltd | |