| NRC Kept AS | Construction | 2011 |
| NRC Maskin Holding AS | Construction | 2019 |
| NRC Norge AS | Construction | 2014 |
| NRC Norge Holding AS | Construction | 2011 |
| NTT Security (Norway) AS | Information & communication | 1986 |
| Ny Arena AS | Professional & scientific | 2009 |
| Nybaco Eiendom 1 AS | Real estate | 2022 |
| Nydalsveien 36 AS | Real estate | 2000 |
| Nydalsveien 38 AS | Real estate | 2000 |
| Nye Gol 5/448 AS | Real estate | 2021 |
| Nye KM Aviatrix Invest AS | | 2018 |
| Nye Storebrand Haakon Vii's Gate 10 AS | Real estate | 2025 |
| Nye Storebrand Kjøpesenter City Syd II AS | Real estate | 2018 |
| Nye Storebrand Kjøpesenter Kvadrat AS | Real estate | 2025 |
| Nye Storebrand Lysaker Torg 5 - 25 AS | Real estate | 2018 |
| Nye Storebrand Ruseløkkveien 14 AS | Real estate | 2021 |
| Nye Storebrand Sjøgata 4 AS | Real estate | 2025 |
| Nygård Næringseiendom AS | Real estate | 2011 |
| Nøtholmen Hotelleiendom AS | Real estate | 2004 |
| O.B. Sørensen & Co AS | Financial services | 2007 |
| Obb Holding AS | | 2023 |
| Observatory Aviation Assets AS | Administrative & support | 2026 |
| Obw-Rubb International AS | Construction | 2009 |
| Ocean Sun AS | Professional & scientific | 2016 |
| Ocean Sun Systems AS | Professional & scientific | 2019 |
| Ocean Yield Advisors AS | Professional & scientific | 2018 |
| Ocean Yield AS | Transport & logistics | 2007 |
| Ocy Armada AS | Administrative & support | 2025 |
| Ocy Gallivat AS | | 2024 |
| Ocy Natgas AS | | 2025 |
| Odin Konsult AS | Information & communication | 2015 |
| Odontoclinica AS | Health & social care | 2018 |
| Odyssey Import Ans | Wholesale & retail | 2004 |
| Odyssy AS | Financial services | 1994 |
| Office Control Holding AS | Wholesale & retail | 2024 |
| Ojiaku Capital AS | | 2025 |
| Old Kværner Invest AS | Mining & quarrying | 1987 |
| Ole Loga AS | Construction | 2023 |
| Olsen Eiendom AS | Real estate | 1987 |
| Oma Vin AS | Wholesale & retail | 2020 |
| Omny AS | Information & communication | 2022 |
| Omny Holding AS | Information & communication | 2022 |
| On Food Norway AS | Hospitality | 2007 |
| Onesubsea AS | Mining & quarrying | 2022 |
| Opplysningen 1881 AS | Administrative & support | 2010 |
| Oracle Corporation Canada Inc | Information & communication | 2009 |
| Oracle Emea Limited | Wholesale & retail | 2002 |
| Oracle Global Services Norway AS | Information & communication | 2019 |
| Oracle Norge AS | Information & communication | 1986 |
| Oracle Slovensko Spol S.R.O. | Administrative & support | 2013 |
| Oracle Svenska AB | Professional & scientific | 1999 |
| Orange Cyberdefense Norway AS | Information & communication | 2000 |
| Orbis Wines AS | Wholesale & retail | 2016 |
| Org Geophysical AS | Professional & scientific | 2001 |
| Origon AS | Professional & scientific | 2024 |
| Origon Holding AS | Professional & scientific | 2024 |
| Orion JBT AS | Construction | 2023 |
| Orm Holding AS | Professional & scientific | 2016 |
| Oro Invest AS | Information & communication | 2013 |
| Ortho-Clinical Diagnostics Norway Nuf | Wholesale & retail | 2016 |
| Ortomedic AS | Wholesale & retail | 1986 |
| Oscarsgate 44 AS | Real estate | 2020 |
| Oslo Airport Village AS | Real estate | 2017 |
| Oslo Brannvern Og Sikring Ans | Education | 2002 |
| Oslo Båtpleie Og Krympeplast AS | Manufacturing | 2026 |
| Oslo Consulting Group AS | Professional & scientific | 2001 |
| Oslo Malerteknikk AS | Construction | 2022 |
| Oslo Revisjon AS | Professional & scientific | 1985 |
| Oslo Shipbrokers AS | Transport & logistics | 2007 |
| Oslo Vann & Varme AS | Construction | 1992 |
| Osram AS | Information & communication | 2015 |
| Ourom Invest AS | Financial services | 2005 |
| Oxe Kapital AS | | 2020 |
| Oxe Prosjekt AS | Professional & scientific | 2021 |
| Paag Eiendom AS | Real estate | 2019 |
| Padel Holdco AS | Arts & recreation | 2022 |
| Padelon AS | Arts & recreation | 2020 |
| Pandora Norge AS | Wholesale & retail | 2010 |
| Paradigme Adr AS | Education | 2022 |
| Paradigme AS | Professional & scientific | 2012 |
| Paradigme Holding AS | Education | 2012 |
| Paradigme Økonomi AS | Professional & scientific | 2013 |
| Paragon Gruppen AS | | 2005 |
| Parc Bidco AS | Arts & recreation | 2019 |
| Parc Holdco AS | Arts & recreation | 2019 |
| Parc Topco AS | Arts & recreation | 2019 |
| Parkvegen Nord AS | Real estate | 2018 |
| Parley 10 AS | Professional & scientific | 2010 |
| Pearl Extend AS | Wholesale & retail | 2019 |
| Pearl Group AS | Information & communication | 2006 |
| Pearl Investco AS | Information & communication | 2020 |
| Pearl Norge AS | Information & communication | 2017 |
| Pearl Resources AS | Information & communication | 2015 |
| Pearl Topco AS | | 2020 |
| Pearlconvert AS | Information & communication | 2011 |
| Pecan Energies Services Nuf | Professional & scientific | 2024 |
| Pel Invest AS | Real estate | 2007 |
| Pelagus 3D AS | Wholesale & retail | 2023 |
| Per Sverres Budservice AS | Transport & logistics | 2020 |
| Personalsykler Norge AS | Administrative & support | 2021 |