| Oliver Duis | Hamburg |
| Oliver F. Lehmann, PMP | Bavaria |
| Oliver Greifenberg | Brandenburg |
| Oliver Hurth e.K. Software-Entwicklung und IT-Service | Saarland |
| Oliver Kreischer | North Rhine-Westphalia |
| OllyDbg | Brandenburg |
| OlufsOffice edv-service | Hamburg |
| Olympus Soft Imaging Solutions GmbH | North Rhine-Westphalia |
| Olysoft e.K. | North Rhine-Westphalia |
| OMEGA Software GmbH | Baden-Württemberg |
| OmegaSoftware | |
| Omikron Data Quality GmbH | Baden-Württemberg |
| Omio | |
| Omiqa Bioinformatics GmbH | |
| Omix Visualization GmbH & Co. KG | North Rhine-Westphalia |
| OMM Solutions GmbH | |
| omni:us | |
| OmniBot GmbH | |
| Omnidat GmbH | Baden-Württemberg |
| Omnidea-RTG | |
| omniIT GmbH | Bavaria |
| Omnis Power | |
| Omniscale GmbH & Co. KG | Lower Saxony |
| OmniSys Informationstechnologien GmbH & Co. KG | |
| Omoo Medienagentur GmbH | Hesse |
| OMS Open Media System GmbH | |
| OMS-Online Marketing Service GmbH & Co. KG | North Rhine-Westphalia |
| OMZ Software | Berlin |
| omz:software | Berlin |
| On-apply GmbH | |
| Onacy GmbH | |
| Oncgnostics GmbH | |
| Oncolead GmbH & Co. KG | |
| ONConsulting GmbH | |
| Ondics GmbH | Baden-Württemberg |
| one by one EDV-GmbH | Berlin |
| One Medialis GmbH | |
| one4vision GmbH | Saarland |
| OneFootball | Berlin |
| OneFor Holding GmbH | |
| onehundreddigital GmbH | Berlin |
| Onelio GmbH | |
| OneSeek.de | Bavaria |
| Onestop Software | |
| OneVision Software AG | Bavaria |
| onFire digital UG (haftungsbeschränkt) | Saxony |
| Onformative GmbH | |
| OnGoingMedia GmbH | |
| onion.net | North Rhine-Westphalia |
| ONIQ GmbH | |