| Symbol | Name | Country | Exchange |
|---|---|---|---|
| NWXPF | Newport Exploration | US | OTC |
| NXGM | NexGen Mining Incorporated | US | OTC |
| NXXGF | Nexus Gold Corp | US | OTC |
| OBGRF | Orbit Garant Drillin | US | OTC |
| OCANF | Oceanagold Corp. | US | OTC |
| OCLDF | Orica Limited | US | OTC |
| OCLDY | Orica Limited | US | OTC |
| OIIIF | O3 Mining Inc | US | OTC |
| OLVRF | Olivut Res Ltd | US | OTC |
| OMMSF | Omineca Mng & Metals | US | OTC |
| ONSS | Onassis Mining Group Inc | US | OTC |
| OODH | Orion Diversified Holding Co. Inc | US | OTC |
| OOGI | C2E Energy, Inc | US | OTC |
| ORAGF | Oremex Res Inc | US | OTC |
| ORESF | Orestone Mining Corp | US | OTC |
| ORMNF | Orex Minerals Inc. | US | OTC |
| OROXF | Orosur Mining Inc | US | OTC |
| ORVMF | Orvana Minerals Corp | US | OTC |
| OSTO | Original Sixteen To | US | OTC |
| OUKPF | Metso Outotec Oyj | US | OTC |