| Sistemas Informáticos de Negocio, S.L. | Madrid |
| Sistemas Informáticos Europeos, S.L. | Madrid |
| Sistemas Master Magazine | Barcelona |
| Sistematic Informática | Valladolid |
| Sitelicon Web Projects, S.L. | Madrid |
| Sitka Capital | Barcelona |
| Six Group | Madrid |
| SiX Informàtics S.C.P. | |
| Sixphere Technologies | |
| Sixtemia | Girona |
| Skura | Gipuzkoa |
| Skydone Solutions, S.L. | Valencia |
| Slashmobility, S.L. | |
| SLCLAB Informática, S.L. | Salamanca |
| Slidesgo | |
| Slimbook | |
| SlottMedia | Madrid |
| SM2 Software Services Management | Balearic Islands |
| Smart Analytics, S.L. | Madrid |
| Smart Point | Barcelona |
| Smart Protection, S.L. | Madrid |
| SmartBits | Madrid |
| Smartbrand, S.L. | Biscay |
| Smartech Capital | Barcelona |
| SmartHC | Madrid |
| SmartMind | Madrid |
| Smartvel | Madrid |
| Smooth Step Web Design | Málaga |
| SMOWLTECH | Gipuzkoa |
| Snab | Madrid |
| SNAP | Barcelona |
| Social Labs | |
| Social Nest Foundation | |
| Social Point, S.L. | Barcelona |
| Sociedad Española de Matemática Aplicada | Madrid |
| Société Générale, Sucursal en España | |
| Socilen PFP, S.L. | Madrid |
| Soelca Laboral, S.A. | Burgos |
| Sofecom | Madrid |
| Sofistic Cybersecurity | Castellón |
| Sofitec Aero, S.L. | |
| Soft Élite | Murcia |
| Soft For You | Barcelona |
| Soft Line Informática | Balearic Islands |
| Softcare Asset Management | Madrid |
| Softcasting | Castellón |
| SoftDoit, S.L. | Barcelona |
| Softeng | Barcelona |
| SoftGalia Aplicaciones Informáticas | Lugo |
| Softme | |