| S-Clinica | |
| S.I. Group S.A. | Liège |
| SABCA | |
| Salesflare | |
| Sanaware Itsana B.V.B.A. | Flemish Brabant |
| Sanel N.V. | Antwerp |
| Santero Therapeutics S.R.L. | |
| SarrCom.com | Antwerp |
| Satbeams S.P.R.L. | Walloon Brabant |
| Satrabel | Walloon Brabant |
| Savaco | West Flanders |
| SBS | |
| ScaleFund | |
| Scarabee Graphic Design | West Flanders |
| Scarlet | Brussels-Capital |
| Schrijf.be | Antwerp |
| SCIA N.V. | Limburg |
| Science Parks of Wallonia | Namur |
| Sciensano | |
| Scientia Terrae Research Institute | |
| SCK CEN | |
| ScriptBook N.V. | Antwerp |
| SD Worx | |
| SDP | East Flanders |
| Seaters | |
| Sébatien Lenaerts | |
| SEE Telecom | Walloon Brabant |
| Seety | |
| Segments.ai | |
| SeJo IT | |
| Selection Computer Distribution | Brussels-Capital |
| Selligent | Walloon Brabant |
| Sematix IT Services | Hainaut |
| Semopti | |
| Sensifai | Brussels-Capital |
| Sensolus | |
| Sentiance N.V. | |
| SEO Dreams | Antwerp |
| Seodvize B.V.B.A. | West Flanders |
| Septentrio | |
| Seqalis | |
| Sequana Medical N.V. | |
| Serico Solutions | |
| ServersCheck B.V. | Walloon Brabant |
| Service de médiation pour les télécommunications | Brussels-Capital |
| Services Informatiques pour Professionnels | Hainaut |
| Servico B.V.B.A. | Antwerp |
| Servilux | Limburg |
| SettleMint | |
| Sewan Groupe | |