| OutThink | |
| Oval Medical Technologies Ltd | |
| Oval Systems Ltd | |
| Overclockers UK | Staffordshire |
| OverDone, LLP | |
| Overleaf | |
| Overmind | |
| Overoptic Systems Ltd | Dorset |
| Overt Software Solutions Ltd | |
| Overture | East Sussex |
| Overture Ltd | Oxfordshire |
| Ovo Spaces | |
| OWA Digital Ltd | Oxfordshire |
| Owiwi | |
| OWLR Technologies Ltd | |
| Owlstone Medical Ltd | |
| Owtanet Ltd | Bristol |
| OX365 | |
| Oxa Autonomy Ltd | |
| OXECO Ltd | |
| Oxehealth | |
| Oxford Apple & Mac Users Group | Oxfordshire |
| Oxford BioDynamics plc | |
| Oxford Biomedica plc | |
| Oxford Brain Diagnostics Ltd | |
| Oxford Brookes University | Oxfordshire |
| Oxford Brookes University - School of Engineering, Computing and Mathematics | Oxfordshire |
| Oxford Business College | |
| Oxford Cancer Biomarkers | |
| Oxford Computer Consultants Ltd | Oxfordshire |
| Oxford Drug Design | Oxfordshire |
| Oxford Endovascular Ltd | |
| Oxford Expression Technologies Ltd | |
| Oxford Gene Technology IP Ltd | |
| Oxford Healthtech Labs | |
| Oxford Home IT Support | Oxfordshire |
| Oxford Immunotec Ltd | |
| Oxford Innovation Ltd | |
| Oxford Innovation Space | |
| Oxford Institute for Energy Studies | |
| Oxford Instruments | |
| Oxford Ionics Ltd | |
| Oxford Mac Solutions Ltd | Oxfordshire |
| Oxford Martin School | |
| Oxford Nanoimaging Ltd | |
| Oxford Nanopore Technologies plc | |
| Oxford Robotics Institute | |
| Oxford Science Park | Oxfordshire |
| Oxford Semantic Technologies | |
| Oxford Space Systems | |