| Sipgate GmbH | North Rhine-Westphalia |
| siQnet Consulting GmbH | |
| SIRADOS | Bavaria |
| Sirana Pharma GmbH | |
| Sirconic Group GmbH | Bavaria |
| SIRION Biotech GmbH | |
| SIRIUS GmbH | Baden-Württemberg |
| Sirius Venture Partners GmbH | Hesse |
| Sirius-net GmbH | Baden-Württemberg |
| SISTRIX GmbH | North Rhine-Westphalia |
| SISU.team | |
| SIT GmbH | North Rhine-Westphalia |
| SIT System- und Informations-Technik GmbH | North Rhine-Westphalia |
| Site Point GmbH | Saarland |
| Site-Optimierer | |
| SITECH Deutschland GmbH | |
| Sitefactor | Baden-Württemberg |
| SiteForce | Bavaria |
| Siteform | Berlin |
| Sitemind Medien Agentur | Lower Saxony |
| SiteOS AG | Bavaria |
| Sitewaerts GmbH | North Rhine-Westphalia |
| Siteway | Hamburg |
| Siticom GmbH | |
| siTOOLs Biotech GmbH | |
| SituatiVe GmbH | |
| SIV AG | Mecklenburg-Vorpommern |
| SIVA creative media | Bavaria |
| SIVIS GmbH | Baden-Württemberg |
| Siwa Bürotechnik IT GmbH | |
| Siwalu Software GmbH | |
| SIX | |
| Sixonia Tech GmbH | |
| SIZ GmbH | North Rhine-Westphalia |
| Sizekick | |
| SJ Software GmbH | North Rhine-Westphalia |
| SK Trade GmbH | Bavaria |
| SK-Electronik GmbH | North Rhine-Westphalia |
| Skamper Kommunikation | North Rhine-Westphalia |
| skdesign Kamphuis & Kosub GbR | North Rhine-Westphalia |
| sked software GmbH | North Rhine-Westphalia |
| Skeleton Technologies | |
| SkenData GmbH | |
| Skill Networks Solutions Factory GmbH | |
| Skill Software GmbH | |
| Skilllocation GmbH | North Rhine-Westphalia |
| Skillnet GmbH | |
| SKS Soft GmbH | North Rhine-Westphalia |
| Skullbyte | North Rhine-Westphalia |
| Skulteky Elektronik GmbH | North Rhine-Westphalia |