| Open Society Foundations (OSF) |
| Open University |
| OppenheimerFunds |
| Opportunity Bank |
| Options Consultancy Services |
| Oracle Corporation |
| Oracle Corporation UK Limited |
| Orange Organisation |
| Orange Tunisie SA |
| Orascom Construction Plc |
| Orascom Group |
| Org Beverages SARL |
| Organic Seed & Bean Co Ltd |
| Organisation for the Professional Empowerment of Women |
| Orient Productions |
| Orkla |
| Orkla ASA |
| Ornua Co-operative Limited |
| Oromia Insurance S.C. |
| Orveon |
| Out of the Box |
| Outdoor & Sports Company (OSC) Limited |
| Outsider |
| OVO Group Ltd [Formerly Ovo Energy (Group)] |
| Oxfam Activities Limited (OAL) |