| Nitor Vital AS | Health & social care | 2017 |
| Njord Clean Air Norge AS | Professional & scientific | 2019 |
| NKS Østbytunet AS | Health & social care | 2005 |
| NM Tjenester AS | Construction | 2025 |
| Nodu AS | Transport & logistics | 2024 |
| Noli Renhold Og Vedlikehold AS | Administrative & support | 2021 |
| Nor Fusion AS | Professional & scientific | 2022 |
| Nor Holding AS | | 2023 |
| Nor Properties AS | Real estate | 2020 |
| Nor Secure AS | Administrative & support | 2012 |
| Nor Securities AS | Wholesale & retail | 2016 |
| Nord Import AS | Wholesale & retail | 2025 |
| Nordberg Invest AS | Financial services | 2005 |
| Nordbyhagen Mat AS | Wholesale & retail | 2001 |
| Nordic American AS | Professional & scientific | 2016 |
| Nordic Camping Da | Administrative & support | 2025 |
| Nordic Carpathian Snekker AS | Construction | 2026 |
| Nordic Event Rentals AS | | 2026 |
| Nordic Kitchen Studio AS | Wholesale & retail | 2025 |
| Nordic Medical AS | Health & social care | 2022 |
| Nordic Mineral AS | Wholesale & retail | 2026 |
| Nordicsafe AS | Health & social care | 2016 |
| Nordpole AS | Wholesale & retail | 2026 |
| Nordri AS | Construction | 2021 |
| Nordri Entreprenør AS | Construction | 2023 |
| Nordri Holding AS | Construction | 2023 |
| Nordstrand Kampsportsenter AS | Arts & recreation | 2016 |
| Nordstrand Steinbrudd AS | Real estate | 2023 |
| Norecon AS | Construction | 1984 |
| Norges Takst AS | Real estate | 2005 |
| Norges Takst AS | | 2026 |
| NORHOLM1 AS | Real estate | 2020 |
| Norindia AS | Hospitality | 2025 |
| Normann Finans AS | Real estate | 1998 |
| Normann Industriservice AS | Wholesale & retail | 2000 |
| Normeca International AS | Wholesale & retail | 1997 |
| Norspeed AS | Transport & logistics | 2024 |
| North Web AS | Information & communication | 2015 |
| Northpoint AS | Information & communication | 2024 |
| Northsoft AS | Information & communication | 2022 |
| Nortur Logistikk AS | Transport & logistics | 2022 |
| Norvex Frakt AS | Transport & logistics | 2026 |
| Norwegian Ground AS | Real estate | 2015 |
| Notim AS | Wholesale & retail | 1999 |
| Notim Holding AS | Wholesale & retail | 2023 |
| Nova Bilpleie AS | Other services | 2023 |
| Nova Renhold Sukran Arslankaya Ans | Administrative & support | 1998 |
| Nova-Ren AS | Administrative & support | 2012 |
| Nra Øst AS | Construction | 2012 |
| NT Regnskap AS | Professional & scientific | 2007 |
| Nuevo Bolig AS | Real estate | 2021 |
| Nye Skippern Ans | Hospitality | 1991 |
| Næringsbygg AS | Real estate | 1984 |
| Nøkkelsikringen Da | Administrative & support | 1995 |
| O.K. Andersen Byggautomasjon AS | Professional & scientific | 2012 |
| O2 Holding AS | Health & social care | 2016 |
| Off Course Holding AS | | 2007 |
| Oioi AS | Professional & scientific | 2019 |
| Oioi Drift AS | Administrative & support | 2020 |
| Oioi Eiendom AS | Professional & scientific | 2020 |
| Oioi Grorudveien AS | Real estate | 2019 |
| Oioi Næring AS | Real estate | 2016 |
| Oioi Odalsgata 47 AS | Real estate | 2009 |
| Oioi Sørumsandveien 45 AS | Real estate | 1997 |
| Ole Closs AS | Health & social care | 2014 |
| Onda Norge AS | Wholesale & retail | 2019 |
| One Percent AS | Wholesale & retail | 2026 |
| Opta Eiendom AS | Real estate | 2016 |
| Oreb 2 AS | Construction | 2026 |
| Origami Studios AS | Professional & scientific | 2020 |
| Orntlimusikk Ans | Information & communication | 2021 |
| Orthecta AS | Professional & scientific | 2021 |
| Os Transport AS | Transport & logistics | 1997 |
| Oslo Blaaseorkester SA | Arts & recreation | 2023 |
| Oslo Bygg Maler AS | Construction | 2015 |
| Oslo College of Managment Da | Education | 2013 |
| Oslo Dance & Fitness Store Ans | Wholesale & retail | 2008 |
| Oslo Elektro & Rør AS | Construction | 2019 |
| Oslo Felgretting AS | Other services | 2024 |
| Oslo Flytte- Og Renholdservice AS | Transport & logistics | 2024 |
| Oslo Og Viken Turbusser AS | Transport & logistics | 2020 |
| Oslo Plumbing Holding AS | | 2023 |
| Oslo Rørlegger & Entreprenørbedrift AS | Construction | 2007 |
| Oslo Vindtunelldrift AS | Education | 2023 |
| Oterholt Holding AS | | 2016 |
| Otto Mobility AS | Administrative & support | 2015 |
| Ouissar Blikkenslager AS | Construction | 2025 |
| Ovnero AS | | 2025 |
| Ovt Gruppen AS | Transport & logistics | 2024 |
| Oysbir AS | | 2025 |
| Paadrift AS | Hospitality | 2022 |
| Pallebua AS | Wholesale & retail | 2002 |
| Parkveien 27-31 AS | Real estate | 2023 |
| Parkveien Utvikling AS | Real estate | 2017 |
| Paulius Invest AS | Financial services | 2016 |
| Pearson Education Ltd | Information & communication | 2009 |
| Pedagogene Ans | Information & communication | 2023 |
| Pelly Butikkinnredning AS | Wholesale & retail | 2012 |
| Per Sigtun AS | Wholesale & retail | 1975 |
| Pereco Holding AS | Real estate | 2001 |