| Sprama Game Labs S.r.l. | Cagliari |
| SPS S.r.l. | Bologna |
| Spusu Italia S.r.l. | Milan |
| Sputnix.it | Palermo |
| Square Marketing S.r.l. | |
| Squized Internet Solutions | Barletta-Andria-Trani |
| SSE S.p.A. | |
| Stacec S.r.l. | Reggio Calabria |
| Stal S.n.c. | Rome |
| Stam S.r.l. | Genoa |
| Star Capital SGR S.p.A. | |
| Star Tech Ventures | |
| STAR7 S.p.A. | |
| Starsoftware Group | Venice |
| Startalia S.r.l. | Rome |
| Startgram | |
| Starting Finance S.r.l. | |
| Startup Bakery S.r.l. | |
| Startup Business | Milan |
| Startup Club | Bari |
| Startup Geeks | Mantua |
| Startup Network S.r.l. | |
| StartUP.News.it | Milan |
| StartupGym Studio S.r.l. | |
| StartupItalia Open Summit | Cagliari |
| StartupItalia S.r.l. | Milan |
| Stazione Sperimentale del Vetro SCPA | |
| Ste S.r.l. | Milan |
| Stefano Cassone Web Design | |
| Stelda Informatica S.r.l. | Como |
| Stellantis Financial Services Italia | |
| Stellar Recupero Dati | Milan |
| Steltronic S.p.A. | Brescia |
| Stelvio S.p.A. | Lecco |
| Stema S.r.l. | |
| StemGen S.p.A. | |
| STEP 4 Business | Milan |
| Step S.r.l. | |
| Step Venture | |
| StephenSoftware S.r.l. | Rome |
| Steps Connect | |
| Steroglass S.r.l. | |
| Stetel S.r.l. | Livorno |
| Stiantos | Lucca |
| Stip S.r.l. | |
| Stol Computer S.r.l. | Pesaro and Urbino |
| Store360 | Genoa |
| Storeis S.r.l. | |
| Stormind Games | |
| Storykube S.r.l. | Rome |