| OSTHUS GmbH | North Rhine-Westphalia |
| Ostrom | |
| OSTWALD GmbH | |
| OSY GmbH | Baden-Württemberg |
| OSYON GmbH | Berlin |
| Otark GmbH | |
| Otris Software AG | North Rhine-Westphalia |
| OTRS AG | |
| OTS Informationstechnologie AG | Bavaria |
| OTT Software - mobile solutions | Bavaria |
| ott-deffge ITconsulting | Berlin |
| Otten Software GmbH | North Rhine-Westphalia |
| Otto Group Solution Provider GmbH | Saxony |
| Otto Krahn Group GmbH | |
| Otto Salzer 3D | Baden-Württemberg |
| Otto-Friedrich-Universität Bamberg | |
| Otto-von-Guericke-Universität - Fakultät für Informatik | Saxony-Anhalt |
| Otto-von-Guericke-Universität Magdeburg | |
| Otto-von-Guericke-Universität Magdeburg - Fakultät für Mathematik | Saxony-Anhalt |
| Ottobock | |
| Ottonova Holding AG | |
| Outertech e.K. | |
| Outline - Online Medien GmbH | Bavaria |
| Outline Development | North Rhine-Westphalia |
| Outsourcing Destination Guides | |
| OV-IT Oelker & Volz Computer GmbH | Hesse |
| Overland Tandberg | North Rhine-Westphalia |
| Övermöhle Consult & Marketing GmbH | |
| OVERW8 | |
| OVH GmbH | Saarland |
| OVSoftware GmbH | North Rhine-Westphalia |
| OWH SE i.L. | |
| OWIS GmbH | Baden-Württemberg |
| Own-Free-Website.com | Bavaria |
| ownCloud GmbH | Bavaria |
| OWNLY FinTech GmbH | |
| ownSoft | North Rhine-Westphalia |
| OWWN | |
| Oxacell AG | |
| OXID eSales AG | Baden-Württemberg |
| Oxid Forge | |
| Oxolo GmbH | |
| Oyster Bay Venture Capital GmbH & Co. KG | |
| Oz GmbH | Baden-Württemberg |
| P & H Datentechnik GmbH | Lower Saxony |
| P&I Personal & Informatik AG | Hesse |
| P&P Software | Lower Saxony |
| P&PM Solutions & Consulting GmbH | |
| P&S Fichtner IT Consulting GmbH | North Rhine-Westphalia |
| P+E Prozesstechnik+Elektronik | Hesse |