| Object International Software | Baden-Württemberg |
| ObjectFab GmbH | Saxony |
| Objective MicroSystems oHG | Hesse |
| Objective Networking | |
| Objective-Basic | Hesse |
| Objectpark Software Theisen & Katerbau GbR | North Rhine-Westphalia |
| Objektorientierte Software Entwicklung | Lower Saxony |
| OBM-Media e.K. | North Rhine-Westphalia |
| Obotritia Capital KGAA | |
| OBS Bürocentrum GmbH | Saxony |
| Obsidium Software | |
| Obtiv e.K. | Rhineland-Palatinate |
| OC Projects, Optendrenk & Calinski GmbH | North Rhine-Westphalia |
| Ocean Consulting GmbH | Berlin |
| Oceanis | |
| OCELL GmbH | |
| ochschule Ravensburg-Weingarten | |
| OCM Software | Bavaria |
| OCR2Edit | |
| OCT Clinical | |
| OctaVIA AG | Hesse |
| Oculai GmbH | |
| Oculavis GmbH | |
| Oculeus GmbH | |
| OdiSys GmbH | |
| ODS Gesellschaft für Datenbanksysteme mbH | Berlin |
| ODU GmbH & Co. KG | Bavaria |
| OEB | Berlin |
| Oehler Regeltechnischer Service GmbH | Saxony |
| oeko.net Mueller & Brandt GbR | North Rhine-Westphalia |
| Offene Systeme Software! | Baden-Württemberg |
| OFFIS e.V. | |
| OGS Gesellschaft für Datenverarbeitung und Systemberatung mbH | Rhineland-Palatinate |
| oh22information services GmbH | |
| OHB COSMOS International Launch Services GmbH | |
| OHB Digital Services GmbH | Bremen |
| OHB SE | Bremen |
| OHB System AG | Bremen |
| OHB Venture Capital GmbH | |
| Ohmtech.io | |
| OIO Competence Center | Baden-Württemberg |
| OKAP:Orbits GmbH | |
| Okapost GmbH | Baden-Württemberg |
| OKO-tech GmbH & Co. KG | |
| Ökorenta Invest GmbH | Lower Saxony |
| oktoNet GmbH | |
| Ökumenisches Hainich Klinikum gGmbH | |
| Olaf Bertsche und Bettina Spiegel GbR | Baden-Württemberg |
| Olbisoft GmbH | Lower Saxony |
| olemedien | webdesign aus hamburg | Hamburg |