| Circuly GmbH | |
| Cirillo Consulting GmbH | |
| 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 | |
| Claimsforce GmbH | Hamburg |
| Claneo | |
| Clanq AG | |
| Claranet GmbH | Hesse |
| CLARIN-D | |
| Clarity & Success Software GmbH | North Rhine-Westphalia |
| Clarity AG | Hesse |
| Clark Germany GmbH | Hesse |
| Clasen Datensysteme GmbH | Rhineland-Palatinate |
| Classix Software GmbH | Hamburg |
| ClassWizard GmbH | Hamburg |
| Claudia und Andreas Unkelbach | Hesse |
| Claw Design Software | Baden-Württemberg |
| CLC Unternehmensberatung für Logistik GmbH | Baden-Württemberg |
| Clean Code Developer | |
| Clearingstelle | Baden-Württemberg |
| Clearline Design | Schleswig-Holstein |
| Clemens GmbH | Bavaria |
| Clever + Zöger GmbH | North Rhine-Westphalia |
| Clever Elements GmbH | Berlin |
| Cleverbridge | North Rhine-Westphalia |
| Cleverbridge AG | North Rhine-Westphalia |
| CleverReach GmbH & Co. KG | |
| Cleversoft GmbH | Bavaria |
| Cleverworks | Hesse |
| Clevver GmbH | |
| CLiB Computerlösungen im Bauwesen GmbH | Hamburg |
| Click Effect | Baden-Württemberg |