| Nova Begravelsesbyrå AS | | 2025 |
| Nova Fama AS | Information & communication | 2026 |
| Novaform AS | Professional & scientific | 2007 |
| Novorender AS | Information & communication | 2016 |
| Novu Invest AS | Professional & scientific | 2017 |
| NPT AS | Professional & scientific | 2002 |
| NQM Consulting AS | Professional & scientific | 2024 |
| NT Products AS | Manufacturing | 2017 |
| Nuaer AS | Professional & scientific | 2021 |
| Numinex AS | Real estate | 2013 |
| Nut Holding AS | Professional & scientific | 2022 |
| Nut Kommunikasjon AS | Professional & scientific | 2013 |
| Nuto AS | Information & communication | 2024 |
| Nye Capnor Mor AS | | 2025 |
| Nye Frisøren AS | Other services | 2024 |
| Nye Monoddveien 5 AS | Real estate | 2020 |
| Nye Sabrura Kvadrat AS | Hospitality | 2025 |
| Nygaard Og Idland AS | Construction | 2024 |
| Nygaardshagen Næring AS | Real estate | 2013 |
| Nygård & Sønner Utvikling AS | Real estate | 2022 |
| Nygårdshusene AS | Real estate | 2015 |
| Nyland Byggeadministrasjon AS | Professional & scientific | 1984 |
| Nymark VVS AS | Construction | 2024 |
| Nyp 2 AS | Transport & logistics | 2017 |
| Nysted Eiendom AS | Real estate | 1999 |
| Nysted Eiendom Holding AS | Real estate | 2024 |
| Nysted Hove AS | Real estate | 2021 |
| Nysted Invest AS | Real estate | 2005 |
| Nysted Proff AS | Real estate | 2010 |
| Nyvoll AS | Financial services | 2011 |
| Nådlandskroken 11 AS | Real estate | 2005 |
| Næringsgården Randaberg AS | Real estate | 1997 |
| Nærland Anleggsteknikk AS | Manufacturing | 2021 |
| Nærland Holding AS | | 2021 |
| Nøste Energi AS | Mining & quarrying | 2004 |
| Nøttveit Invest AS | Information & communication | 2006 |
| O. Kristensen Bygg AS | Construction | 2015 |
| O.C. Østraadt AS | Real estate | 2005 |
| O.C. Østraadt Invest AS | Real estate | 2025 |
| O.J Bygg AS | Construction | 2025 |
| O.R.T. Holding AS | Financial services | 2005 |
| O.Sviland AS | Professional & scientific | 2021 |
| Oakbridge Eiendom AS | Real estate | 2019 |
| Oalsgt 30 AS | Real estate | 2001 |
| Obed AS | Other services | 2005 |
| Obed Begravelsesbyrå AS | Other services | 1977 |
| Obm Holding AS | Financial services | 2024 |
| Obsidian Technology AS | Professional & scientific | 2018 |
| Obstfelder AS | Real estate | 2014 |
| Ocean Rig UK Ltd | Mining & quarrying | 1999 |
| Oceaneering AS | Mining & quarrying | 1973 |
| Octagon Bidco AS | Information & communication | 2021 |
| Ocø Holding AS | | 2025 |
| Odd Fellow Sandnes AS | Real estate | 1997 |
| Odd Helge Askeland Holding AS | | 2020 |
| Odda Kran AS | Administrative & support | 2005 |
| Oddane AS | Real estate | 2005 |
| Odden Holding AS | Financial services | 2011 |
| Oddi-As AS | Construction | 2018 |
| Oddsen-Holding AS | | 2019 |
| Odemto AS | Financial services | 2013 |
| Odin Carbon AS | Professional & scientific | 2022 |
| Odins Lille Design AS | Professional & scientific | 2026 |
| Odle Invest AS | Financial services | 2005 |
| Odnaberget Utviklingsselskap AS | Real estate | 2011 |
| Odonto AS | Wholesale & retail | 2024 |
| Oe Eiendom Holding AS | Real estate | 1999 |
| Oe Gruppen AS | Professional & scientific | 2014 |
| Oe Holding AS | Manufacturing | 2010 |
| Oe Industri Holding AS | Wholesale & retail | 2016 |
| Oe Plast AS | Professional & scientific | 2010 |
| Of Transport AS | Transport & logistics | 2023 |
| Offshore Communication AS | Information & communication | 2015 |
| Offshore Containers AS | Wholesale & retail | 1997 |
| Offshore Trading AS | Wholesale & retail | 2000 |
| Ogna Sider Og Skoghage AS | Manufacturing | 2023 |
| Ogr AS | Administrative & support | 2023 |
| Oh Hemnes AS | Real estate | 2010 |
| Ohmtech AS | Information & communication | 1987 |
| Oilfield Production Support Group Lmimited Nuf | Professional & scientific | 1995 |
| Oj Invest AS | | 2018 |
| Oj Løland Holding AS | | 2023 |
| Ok Invest & Services AS | | 2021 |
| Ok Vedøy AS | Administrative & support | 2022 |
| OK4 Ung AS | Health & social care | 2022 |
| Oker Energy AS | Energy | 2020 |
| Oksafoten Renseanlegg SA | Water & waste | 2017 |
| Oktaeder Invest AS | Real estate | 2000 |
| Oktanten AS | Real estate | 2003 |
| Okto Technologies AS | Information & communication | 2021 |
| Okv AS | Administrative & support | 2005 |
| Ol Eiendom AS | Real estate | 2017 |
| Ol Eiendom Lyseparken AS | Real estate | 2026 |
| Ol Utbygging AS | Real estate | 2022 |
| Ola Og Oline AS | Wholesale & retail | 2023 |
| Ola Svendsen Holding AS | Financial services | 2013 |
| Olav Askeland Holding AS | | 2023 |
| Olav Kyrresgate 2 AS | Real estate | 2016 |
| Olav Larsen Invest AS | Financial services | 2018 |
| Olavs Trafikkskole AS | Education | 1991 |