| ODG Sp. z o.o. | |
| ODL Sp. z o.o. | Masovian |
| OF.pl Sp. z o.o. | Silesian |
| Office & Cowork Centre Sp. z o.o. | |
| Office Sp. z o.o. | |
| OfficeFinder.pl | |
| OFFNET | Lesser Poland |
| OGGO Sp. z o.o. | |
| Okinet S.C. | Lower Silesian |
| Okinet s.c. | |
| OLE Holding Sp. z o.o. | |
| Olicom | Greater Poland |
| Olimpiada Informatyczna | Masovian |
| Olimpiada Matematyczna | Masovian |
| Omegasoft.pl | Silesian |
| Omni Calculator Sp. z o.o. | |
| Omnipack Sp. z o.o. | |
| One Dynamics Sp. z o.o. | |
| One More Level S.A. | |
| One System Sp.z o.o. | |
| one-third of all smartphones | Masovian |
| OneMeter Sp. z o.o. | |
| Onex Group Prosta S.A. | |
| Ongeno Sp. z o.o. | |
| ONIX Consulting Sp. z o.o. | |
| Online Venture Sp. z o.o. | |
| OnlineCRF, LLC | |
| Onteon Tech Sp. z o.o. | |
| Onteon Tech Sp. z o.o. | |
| Onwelo Sp. z o.o. | |
| Onyx Sp. z o.o. | Masovian |
| Opcja Sp. z o.o. | Masovian |
| Opcode.pl | Silesian |
| OpenAlternative | |
| OpenForm | |
| Opennet.pl | Masovian |
| OpenOffice Software Sp. z o.o. | Masovian |
| OPGK Rzeszów S.A. | |
| OPGK Rzeszów S.A. | |
| Opitz Consulting Polska Sp. z o.o. | |
| Oplrint Sp. z o.o. | Lower Silesian |
| Opolnet.com | Opole |
| OpsWay | |
| Optimatik Sp. z o.o. | |
| Optimus Sp. z o.o. | Lower Silesian |
| Optizen Labs | Masovian |
| Optomer | Łódź |
| OPW Doskomp Sp. z o.o. | Łódź |
| Oracle Poland | Masovian |
| Orange Fab Polska | |