| Source Design Consultants | Dublin City Council |
| South East BIC | |
| Sovy Trust Solutions Ltd | |
| SpamTitan Technologies | Galway City Council |
| Spearline Labs Ltd | |
| Speed Fibre Group | |
| Speedchecker Ltd | |
| Spinal Stabilization Technologies Ltd | |
| Spoiled Milk Ltd | Cork County Council |
| SportsTech Ireland | |
| Square Root | |
| Square1 | Dublin City Council |
| Squaredot | Dublin City Council |
| Standard Access | |
| Starling Surgical | |
| Start Monday Ltd | |
| Startup Galway | Galway City Council |
| Startup Ireland | Dublin City Council |
| Startup Journey.ie | |
| Startup Network Europe | |
| StartupLighthouse | |
| StarUps | |
| Statcounter | Dublin City Council |
| Statistical Solutions Ltd | Cork City Council |
| StellaDoradus | Waterford City and County Council |
| Steris | |
| Stocktaking.ie | |
| STORM Web Development Ltd | Tipperary County Council |
| Strencom | Cork City Council |
| Strikepay | |
| Structure101 | Waterford City and County Council |
| Studio9 | |
| SuccessfulSEO | Dublin City Council |
| SuperNode Ltd | |
| Supply Finance | |
| Swappsi Ltd | |
| Swift Web | Dublin City Council |
| Swiftcall | Dublin City Council |
| Switch Business Systems | |
| Symberity | Cork City Council |
| Synergy Centre ITT Dublin | Dublin City Council |
| SynOx Therapeutics Ltd | |
| Sysco Software Solutions | Dublin City Council |
| Systeme.io | |
| Systems Modelling Ltd | Wexford County Council |
| Sysxnet Ltd | Dublin City Council |
| TalentHub | |
| Taoglas | Wexford County Council |
| TASC | Dublin City Council |
| Taxback | |