| Num Nummy AS | Wholesale & retail | 2023 |
| Nummer 23 AS | Professional & scientific | 2014 |
| Nupe AS | | 2020 |
| NVG Holding AS | | 2020 |
| NWK Invest AS | | 2021 |
| Ny Design AS | Construction | 2020 |
| Ny Driv AS | Real estate | 2000 |
| Ny Linje AS | Administrative & support | 1992 |
| Nybakk Fundament AS | | 2026 |
| Nybrygga Eiendom AS | Real estate | 2011 |
| Nye Adams Frisør AS | Other services | 1998 |
| Nye Gestaltakademiet AS | Education | 2016 |
| Nye Granåsen Eiendom AS | Real estate | 2012 |
| Nye Ljosland Fjellstove AS | Real estate | 2022 |
| Nye Mji Mørk & Jacobsen Invest AS | Construction | 2021 |
| Nye PP Datter AS | Real estate | 2022 |
| Nye Sentrumklinikken AS | Health & social care | 2026 |
| Nye Spire Psykologtjeneste AS | Health & social care | 2018 |
| Nye Støleheia Sør AS | Real estate | 2024 |
| Nye Tollbodgata 7 AS | Households | 2026 |
| Nye Veier AS | Construction | 2015 |
| Nygaard Holding AS | Real estate | 2007 |
| Nylund Kreunen AS | Real estate | 2024 |
| Nyordre AS | Information & communication | 2025 |
| Nytenking AS | Professional & scientific | 2010 |
| Nytt Ikke Ubrukt AS | Manufacturing | 2026 |
| Nytt Liv Brukt AS | Wholesale & retail | 2026 |
| Nyvår AS | Administrative & support | 2026 |
| Nortrans Transporter AS | Real estate | 1978 |
| Næringsbox AS | | 2017 |
| Næringsmegleren AS | Real estate | 1997 |
| Næringsvekst Sør AS | Real estate | 1997 |
| Næromsorg AS | Health & social care | 2016 |
| Nørd Music AS | Arts & recreation | 2020 |
| Nøye AS | Professional & scientific | 2015 |
| O&B Invest Sør AS | Health & social care | 2023 |
| O. Sørli Eiendom AS | Construction | 2017 |
| O.E. Holding AS | Financial services | 2005 |
| O.P. Drangsholt Konsulenttjenester AS | Information & communication | 2021 |
| O.T.Eidjord Invest AS | | 2012 |
| Oak Bay Invest AS | | 2025 |
| Oak Mtach AS | | 2021 |
| Oakland Holding AS | | 2016 |
| Oakland Rain AS | Information & communication | 2015 |
| Oasen Media AS | Information & communication | 2013 |
| Oasen Skole Strømme AS | Education | 2012 |
| Oasen Skole Vågsbygd AS | Education | 2014 |
| Oasen Videregående Skole AS | Education | 1996 |
| Ocd AS | Professional & scientific | 2017 |
| Ocd-Components AS | Professional & scientific | 2026 |
| Ocean Cloud AS | Financial services | 2009 |
| Ocean Drone Technology AS | Professional & scientific | 2022 |
| Oceida AS | Financial services | 2014 |
| Ocrea AS | Professional & scientific | 2023 |
| Ocs AS | | 2023 |
| Octagon AS | Professional & scientific | 2015 |
| Octav AS | | 2001 |
| Octavijan AS | Real estate | 2005 |
| Octosec AS | Information & communication | 2020 |
| Oculus Arkitektur AS | Professional & scientific | 2025 |
| Od Invest AS | Real estate | 2005 |
| Odd Fellow Gården Kristiansand SA | Real estate | 1988 |
| Odd Holskog AS | | 1995 |
| Odd Magne Aasheim AS | Construction | 2013 |
| Odd Mjåland Invest AS | | 2018 |
| Oddemarka Auto Holding AS | Other services | 2005 |
| Oddemarka Bilservice AS | Administrative & support | 1993 |
| Oddemarka Vask AS | Other services | 2024 |
| Odden Næringsbygg AS | Real estate | 2000 |
| Odderhei Invest AS | Wholesale & retail | 2005 |
| Oddernes Gartneri AS | Agriculture & fishing | 2003 |
| Oddernes Kolonial AS | Wholesale & retail | 1995 |
| Oddernestun AS | Real estate | 2018 |
| Oddmar Og Eva AS | Financial services | 2011 |
| Oddvar Moy AS | Wholesale & retail | 1991 |
| Ode Tjeldbergodden Holding AS | Agriculture & fishing | 2015 |
| Ode Tømmervåg AS | Agriculture & fishing | 2026 |
| Odin Bolig AS | Real estate | 2021 |
| Odin-Bygg AS | Real estate | 2024 |
| Odin-Entreprenør AS | Real estate | 2023 |
| Odl AS | Professional & scientific | 2016 |
| Odno AS | Real estate | 2010 |
| Odno Holding AS | Real estate | 2010 |
| Oeh Invest AS | | 2021 |
| Offshore Kraft AS | Professional & scientific | 2011 |
| Offshore Norge AS | Wholesale & retail | 2014 |
| Offshore Norge Fund AS | | 2026 |
| Offshore Wind Industries AS | Construction | 2015 |
| Offshorecrew AS | Administrative & support | 2013 |
| Ofh Invest AS | | 2017 |
| Oftenes Vann Og Avløpsforetak SA | Water & waste | 2010 |
| Ogge Eiendom AS | Real estate | 2025 |
| Oggevatn Utvikling AS | Real estate | 2025 |
| Oha Invest AS | Financial services | 2015 |
| Ohoy AS | Information & communication | 2026 |
| Oi Koktelo AS | Wholesale & retail | 2013 |
| Oishi AS | Hospitality | 2014 |
| Ojb Holding AS | Financial services | 2015 |
| Ojfn AS | Wholesale & retail | 2005 |
| Ojj Holding AS | Manufacturing | 2008 |