| Orange Quantum Systems | South Holland |
| Oranje4all Internet | South Holland |
| Orbital Eye | |
| ORCA Therapeutics | |
| OrcaGroup | North Brabant |
| Order-Direct | Flevoland |
| Orderli B.V. | |
| Ordina Nederland | Utrecht |
| Orion Software B.V. | Overijssel |
| Orios | Gelderland |
| Orq.ai | |
| Ortel Mobile | |
| OSC | North Holland |
| Oscaro B.V. | |
| OSN Nederland B.V. | Utrecht |
| OsOffice | Groningen |
| Osteo-Pharma B.V. | |
| Osudio | North Holland |
| OTB Ventures | |
| Otec Finance | South Holland |
| OTIV B.V. | |
| Otoconsult B.V. | |
| Otomi | |
| Otwee B.V. | North Holland |
| OTYS | Utrecht |
| Out of Site | North Brabant |
| OVAS Solutions B.V. | Flevoland |
| Overhoff Telecommunicatie B.V. | Gelderland |
| Override | Flevoland |
| Overstappen.nl B.V. | |
| Overstory | North Holland |
| Overstory | North Holland |
| OVSoftware B.V. | South Holland |
| Owlin | North Holland |
| Owlin B.V. | North Holland |
| OwnIT | Gelderland |
| Oxilion | Overijssel |
| Oxitope Pharma B.V. | |
| OXO Ventures | |
| P-mex Webdesign | North Holland |
| Packaly B.V. | |
| Packard Bell | Gelderland |
| PACT Care B.V. | |
| Pactechno | Utrecht |
| Pakweg.nl | Utrecht |
| Paladin Studios | South Holland |
| Paleo B.V. | |
| PamGene | North Brabant |
| Pan Cancer T | South Holland |
| Panasonic Electric Works Sales Western Europe B.V. | North Brabant |