| CDY | Hainaut |
| CEBEO | West Flanders |
| Cegeka | Limburg |
| Cegid Belgique | |
| Cellaion | |
| Cellistic | |
| Celyad Oncology | |
| Center for Drug Design and Discovery | |
| CentOS | Flemish Brabant |
| CentralApp S.A. | |
| Cerba Research | |
| Cerba Research | |
| CERM | West Flanders |
| CERT-EU | Brussels-Capital |
| CETIC A.S.B.L. | Hainaut |
| Champs-Libres | |
| Chapps N.V. | |
| Cheops | Antwerp |
| Cheqroom | |
| Chili | East Flanders |
| CHILI publish N.V. | |
| Christiaens | West Flanders |
| CISA | |
| Cissoid | Walloon Brabant |
| CitizenLab | Brussels-Capital |
| Citymesh Wireless Networks | West Flanders |
| ClearMedia N.V. | |
| Clef2web | |
| Clevercast | Antwerp |
| CleverPC | East Flanders |
| Clicktouch N.V. | East Flanders |
| Cloud Innovation | |
| Cloudalize | East Flanders |
| Cloudar N.V. | |
| Cluster TIC Infopole | Namur |
| CMR-JET | Flemish Brabant |
| Cobra Technology B.V.B.A. | |
| Coemans.com | Limburg |
| Cohabs | |
| Colibris | Antwerp |
| College of Europe | West Flanders |
| ColmSoft | Antwerp |
| Colruyt Group | |
| Combel N.V. | East Flanders |
| Comeplan | Brussels-Capital |
| Comité Européen de Normalisation Electrotechnique | Brussels-Capital |
| Comperex Belgique S.A. | Flemish Brabant |
| Complidata | |
| Complix | |
| Comptoir Belge de Télécommunications | Brussels-Capital |