| Skipr S.A. | |
| Skwarel S.A. | |
| Skyline Communications | West Flanders |
| Skyscrapers | |
| SLYTIO | Hainaut |
| Smallsites Webdesign | East Flanders |
| Smart Design S.P.R.L. | Walloon Brabant |
| Smartbeam | Brussels-Capital |
| Smartcheckups CommV | |
| SmartConnect N.V. | |
| Smartfin | |
| SmartProjects | Limburg |
| Smartworx | |
| Smovin | |
| Sms ExtraPro | Liège |
| Snijders Compuservice B.V.B.A. | Limburg |
| Snikpic S.R.L. | |
| SOA People | Walloon Brabant |
| Société européenne pour la formation des ingénieurs | |
| Soda Data N.V. | |
| Sodeco N.V. | West Flanders |
| Soft Naert | West Flanders |
| Soft&Log | Liège |
| Softconstruct N.V. | |
| Softo2 | Antwerp |
| Softron Microcomputing S.A. | |
| SoftSign MultiMedia Group | East Flanders |
| Software4U | |
| SOLiTHOR | |
| Sonaca S.A. | |
| Sonal N.V. | Antwerp |
| Sonitron N.V. | East Flanders |
| SOTRAD S.P.R.L. | Walloon Brabant |
| Space Applications Services S.A./N.V. | Flemish Brabant |
| Space Hubs Network | |
| Spacebel | Liège |
| SpaceTec Partners | |
| SpaceTec Partners | |
| Spacewell International | Antwerp |
| Spatie | |
| Spectralys Biotech S.P.R.L. | |
| Spectricity N.V. | |
| SpeechWare | Brussels-Capital |
| Speed.be | Namur |
| Spencer | |
| SPIE Belgium ICS | Walloon Brabant |
| Spikes N.V. | Antwerp |
| SportUp | East Flanders |
| Spott | |
| srtt.be | Liège |