| Novelda AS | Oslo |
| NSN | Oslo |
| NTNU Samfunnsforskning AS | |
| Numascale AS | |
| Numus | |
| Nyby | |
| Nykode Therapeutics ASA | |
| ObjectPlanet, Inc. | Oslo |
| Observe Medical ASA | |
| Ocean Access | |
| Ocean Oasis | |
| Ocean Power Parks | |
| Oddstøl Elektronikk AS | Møre og Romsdal |
| ODI Medical AS | |
| OfficeConsult | Trøndelag |
| Oivi AS | |
| Oliasoft AS | |
| Omega AS | Rogaland |
| Omego Fleet | |
| Oncoinvent ASA | |
| One Call AS | Oslo |
| ONiO | |
| OnNet AS | Oslo |
| Onsagers AS | |
| OnSiteViewer | |
| Opera | Oslo |
| Optimal Norge AS | |
| OptoScale | |
| Oracle Norge AS | Akershus |
| Orbit Systems AS | |
| Orca Labs | |
| Orgdot AS | Oslo |
| Oriented Soft | |
| Orizon | |
| Oslo Business Region | |
| Oslo Edtech Cluster | Oslo |
| Oslo Innovation Week | |
| Oslo International Hub | |
| Oslo Linux User Group | Oslo |
| Oslo Metropolitan University | |
| Oslo Perl Mongers | Oslo |
| Oslo Pils and Linux Users Group | Oslo |
| Oslo universitetssykehus | Oslo |
| Oslo universitetssykehus | |
| OstomyCure | |
| OstomyCure AS | |
| OTee | |
| OTee AS | |
| Otovo AS | |
| Otrum AS | Oslo |