| Oaky B.V. | |
| OAPEN Foundation | |
| Oberon | North Holland |
| Oberst B.V. | |
| OBI4wan B.V. | North Holland |
| Objective Platform | North Holland |
| Ocdlab | |
| Oceans of Energy | |
| Ockto | |
| Odd.Bot B.V. | |
| Oddity.ai | |
| Odournet Holding B.V. | |
| Offensive360 | |
| Office IT | Friesland |
| Offixs | North Holland |
| OGD ict-diensten | South Holland |
| Ohmega Software Platform | South Holland |
| Ohpen | North Holland |
| OJO | |
| Olery B.V. | |
| Olmia Robotics | |
| OLX Group | |
| OMG/Netdirect | |
| Omines | |
| Omni B.V. | |
| OMNI Networks | |
| Omniboost | Zeeland |
| Omnimap | |
| Omnitapps | North Brabant |
| Omnitec | Zeeland |
| ON2IT | |
| Oncolines B.V. | |
| OncoLize | |
| 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 Studio | Groningen |
| Online Creaties | North Brabant |
| Online Marketing Group B.V. | Utrecht |
| Online Strategie | North Brabant |
| Online.nl | North Holland |
| Onlineambitie | |
| Onramper | North Holland |