| Omni B.V. | |
| OMNI Networks | |
| Omniboost | Zeeland |
| Omnimap | |
| Omnitapps | North Brabant |
| Omnitec | Zeeland |
| ON2IT | |
| Oncolines B.V. | |
| Oncosence B.V. | |
| One Display Solution | |
| One Fox | Utrecht |
| One To Watch | |
| OneFit Unlimited B.V. | |
| Onepage.website | South Holland |
| Oneplanetcrowd International B.V. | |
| OneShoe | Utrecht |
| Oneteam | |
| Onetomarket | Gelderland |
| ONI | Groningen |
| Online Creaties | North Brabant |
| Online Marketing Group | Utrecht |
| Online Strategie | North Brabant |
| Online.nl | North Holland |
| Onlineambitie | |
| Onramper | North Holland |
| Onsite Automation | North Holland |
| Ontwerpbureau Dunes | North Holland |
| Onward | North Brabant |
| Onward Consulting | South Holland |
| OOSEOO | Utrecht |
| OPAL Associates B.V. | Gelderland |
| Opatel | South Holland |
| Open Line B.V. | Limburg |
| Open Social | North Holland |
| Open Solution Providers | North Holland |
| Open Source Investor Services B.V. | South Holland |
| Open Universiteit | Limburg |
| Open-I | Utrecht |
| OpenBizz | North Brabant |
| Opencii | Groningen |
| Openeye | Utrecht |
| Openprovider | South Holland |
| OpenSesame ICT B.V. | Utrecht |
| Opentracker | North Brabant |
| OPH | Flevoland |
| Ophtec B.V. | |
| Optics11 Life | North Holland |
| OptimizingPC.com | South Holland |
| Oracle Netherlands | Utrecht |
| Orange Lemon B.V. | North Brabant |