| Christoph Göbel | |
| Christoph Schubert | Bavaria |
| Christophsbad Göppingen | |
| Chromasoft GmbH | Rhineland-Palatinate |
| Chudovo | |
| Chudovo | |
| CHZ-Soft | Lower Saxony |
| CIB software GmbH | Bavaria |
| Cibait AG | Saarland |
| ciconia Systems GmbH | |
| CID GmbH | Hesse |
| CIDEON Holding GmbH & Co. KG | North Rhine-Westphalia |
| CiJu GmbH | Berlin |
| Cilian AG | |
| cimt AG | Hamburg |
| Cineflight GmbH | |
| Cinemo GmbH | |
| Cinference GmbH | |
| Cinteg AG | Baden-Württemberg |
| CINTEG Design Solutions GmbH | Baden-Württemberg |
| CipSoft GmbH | Bavaria |
| Circadian Technologies GmbH | |
| Circle Unlimited AG | Schleswig-Holstein |
| Circula GmbH | |
| circular.fashion | |
| CircularTree | |
| Circulee GmbH | |
| Circuly GmbH | |
| Cirillo Consulting GmbH | |
| Cirrus7 Computing | |
| CiS ELECTRONIC GmbH | North Rhine-Westphalia |
| CIS-Computer GmbH | Rhineland-Palatinate |
| Cisco Systems GmbH | Bavaria |
| CISPA – Helmholtz-Zentrum für Informationssicherheit gGmbH | |
| Ciss TDI GmbH | Rhineland-Palatinate |
| cit GmbH | Baden-Württemberg |
| Citizen Systems Europe GmbH | Baden-Württemberg |
| Cito Transport Technologies GmbH | |
| citroNET | Rhineland-Palatinate |
| City & Bits GmbH | |
| City GmbH | Bavaria |
| City PC | Hesse |
| City Update GmbH | North Rhine-Westphalia |
| CITYCOMP Service GmbH | |
| Civitec | North Rhine-Westphalia |
| cjt Systemsoftware AG | Baden-Württemberg |
| CK Design | Baden-Württemberg |
| CK Software & E-Commerce | North Rhine-Westphalia |
| Claas Agrosystems GmbH & Co. KG | Lower Saxony |
| Claimd GmbH | |