Firma O - Borgen
- Olak AS
- Opsahl Agentur
- Ole Texmo
- Olsen Development
- Ohnstad Bjørn
- Onyszkiewicz Pharadchareephorn
- O Invest AS
- Olak Holding AS
- Odin Invest AS
- Optimal Transport AS
- Obe Holding AS
- Odin Roll-Hansen
- Ola Tollefsen Bussreiser
- Ole Victor Corral
- O-10 Janssen Consulting
- Ole Marius Rygh Design
- Olak Consulting Ola Kvisle
- Oslo Bygg og Interiør Sardina Fraga