Bedrift O - Heimdal
- Oisinvest AS
- Oppmåling AS
- Ob1920
- Ob1920
- Olav Granøien
- Ofstad Invest AS
- Ottos Holding AS
- Oyvindhauge Invest AS
- Oka-Holding AS
- Oksana Breslavski
- Omicron Service AS
- Oslo Bobil
- Opas Holding AS
- O.Mikkelsen AS
- Oil Holding AS
- Oil Eiendom AS
- Olena Kosarieva
- Omicron Automasjon AS
- Ottar Augdal AS
- Orkdal Håndverksservice AS
- Overvik Kompetansesenter
- On Hydraulikk AS
- Omar Fashions
- Ovnsmontør Johnsen
- Olav Spigset
- Ole Lauglo
- Orienteringslaget Trollelg
- Olberg Henning
- Olav Sogn
- Oeg Tegnekontor AS
- Omf Invest AS
- Oddgeir Alstad
- Olav Imset Lien
- Opsahl Eiendom Haugesund AS
- Ole Pettersen Eiendomsselskap AS
- Offshore og Industriprodukt AS
- Oppdal Hiba-Hytter AS
- Otts AS Mateusz Baginiski
- Odd Forseth AS Tlf
- Ole Bjørn Soldal
- Ola Moen Invest AS
- Osteopat Espen Bondø
- Odd Jostein Årbogen
- Ole Jørgensens Veilag
- Oldervoll Line Merethe
- Olavalek Olav Aleksander Myrvang
- O.S. Berg Transport AS
- Orkla Bygg og Anlegg AS
- Opplæringskontoret for Hotell og Restaurantfag i Trøndelag