| Abbreviation | Definition |
|---|---|
| ODYO | Odyssey Energy Limited |
| OEC | Orbital Corporation Ltd |
| OEG | Orpheus Energy Limited |
| OEGO | Orpheus Energy Limited |
| OEL | Ottoman Energy Ltd |
| OEQ | Orion Equities Ltd |
| OEX | Oilex NL |
| OGL | Overseas & General Ltd (Malay CUFS) |
| OGY | Orca Energy Limited |
| OHL | Omnitech Holdings Ltd |
| OIL | Optiscan Imaging Ltd |
| OIP | Orion Petroleum Ltd |
| OKJ | Oakajee Corporation Ltd |
| OKL | Oakland Resources Limited |
| OKN | Oakton Ltd |
| OKU | Oklo Uranium Ltd |
| OKUO | Oklo Resources Limited |
| OLH | Oldfields Holdings Ltd |
| OMH | OM Holdings Ltd |
| OMI | Occupational & Medical Innovatns Ltd |