Bedrift O - Holmen
- Olban AS
- Ourobouros AS
- Orinoco AS
- Ollimac AS
- Ori AS
- Osvold Invest DA
- Odl Invest AS
- Osterhausgate 14 AS
- Oakfield Holding AS
- Oslo Sportsfiskere
- Okto Invest AS
- Odp Holding AS
- Ocean Streams AS
- Oscarsborg Properties AS
- Oscarsborg Eiendomsselskap AS
- Omsøm Astrid Gjerde
- Oslofjorden Capital Management AS
- Online Coach Råheim
- Oslo Functional Fitness Klubb
- Oslo Functional Fitness Klubb
- Oslo Gestalt Terapi -Gl AS