| Name | Type | Country |
|---|---|---|
| CGI | Enterprise | Spain |
| Checkwatt AB | Enterprise | Sweden |
| CIC TOURGUNE | Enterprise | Spain |
| CIRCE | Enterprise | Spain |
| City of Lecce | Public administration | Italy |
| City of Novi Sad | Public administration | |
| Climate Alliance | Enterprise | |
| Cloud’N’Sci Ltd | Enterprise | |
| CM | Enterprise | Spain |
| CodeSyntax | Enterprise | Spain |