| Nubium Systems AS | Information & communication | 2026 |
| NW Holding AS | | 2024 |
| Nye Guttestreker AS | Construction | 2024 |
| Nye Overflater AS | Construction | 2021 |
| Nye Teie Dagligvaredrift AS | Wholesale & retail | 2020 |
| Nynett AS | Real estate | 2005 |
| Nær Invest AS | Real estate | 2005 |
| Nøtterø Gartneri AS | Wholesale & retail | 1997 |
| Nøtterø Sanitetsforening Eiendom AS | Real estate | 2019 |
| Nøtterøy Auto AS | Wholesale & retail | 2004 |
| Nøtterøy Billakkering AS | Other services | 2010 |
| Nøtterøy Bilpleie Da | Other services | 2011 |
| Nøtterøy Båtsenter AS | Manufacturing | 2023 |
| Nøtterøy Eiendom AS | Real estate | 1984 |
| Nøtterøy Elektriske AS | Construction | 2000 |
| Nøtterøy Elektropartner AS | Construction | 2007 |
| Nøtterøy Frukt Og Tobakk Ans | Wholesale & retail | 1988 |
| Nøtterøy Fysioterapi AS | Health & social care | 2019 |
| Nøtterøy Golfbane AS | Arts & recreation | 2000 |
| Nøtterøy Islandshestesenter AS | Education | 2022 |
| Nøtterøy Legesenter AS | Health & social care | 2014 |
| Nøtterøy Ultralydinstitutt Ans | Health & social care | 2000 |
| Nøtterøy Ur & Synssenter AS | Wholesale & retail | 2007 |
| Nøtterøy Ved AS | Agriculture & fishing | 2024 |
| Nøtterøy Vedlikeholdsservice AS | Manufacturing | 2012 |
| Nøtterøyklinikken AS | Health & social care | 2025 |
| O Tjølsen & Sønn AS | Transport & logistics | 1980 |
| O2VIRAGE AS | Professional & scientific | 2024 |
| October Design AS | Professional & scientific | 2010 |
| Odd Bartho-Hansen & Sønner AS | Construction | 1990 |
| Odd Rui AS | Construction | 1996 |
| Oktav AS | Education | 2012 |
| Okura Sushi AS | Hospitality | 2018 |
| Ola Blom AS | | 2019 |
| Olaf B Terjesen AS | Construction | 1984 |
| Ole Gundersen Holding AS | Real estate | 2005 |
| Olsen & Haug Invest AS | | 2025 |
| Omg Prosjekter AS | Construction | 2019 |
| Onor AS | Wholesale & retail | 2019 |
| Onzite AS | Professional & scientific | 2011 |
| Onzite Digital AS | Information & communication | 2017 |
| Opportunity Invest AS | Professional & scientific | 2013 |
| Optima Design AS | Wholesale & retail | 1998 |
| Optura AS | Wholesale & retail | 1958 |
| Optura Nordic AS | Wholesale & retail | 2016 |
| Oriental Food AS | Hospitality | 2023 |
| Oseberg Bolig AS | Real estate | 2018 |
| Oseberg Pharma AS | Wholesale & retail | 2019 |
| Oseberg Services AS | Professional & scientific | 2013 |
| Oslofjordens Kompetansesenter AS | Professional & scientific | 2024 |
| Ottanes AS | Real estate | 2014 |
| Ottestad Bilverksted AS | Other services | 1934 |
| Ottestad Invest AS | | 2025 |
| Outboardspesialisten Marthin AS | Other services | 2006 |
| Ovi Bygg AS | Construction | 2024 |
| Palvin AS | | 2026 |
| Parkvelo AS | Professional & scientific | 2024 |
| Partner Eiendomsdrift AS | Administrative & support | 2018 |
| Paulsen Bygg AS | Construction | 2016 |
| Per Firing AS | Financial services | 2013 |
| Per Johansen AS | Construction | 1983 |
| PGV Invest AS | | 2021 |
| PH Myrvang Holding AS | | 2024 |
| Pha Holding AS | | 2020 |
| Picker AS | | 2021 |
| Pionero AS | Professional & scientific | 2006 |
| Pizza Nuova AS | Hospitality | 2018 |
| Pladsen Holding AS | Financial services | 2013 |
| Plug-In Norge AS | Wholesale & retail | 2014 |
| PMARKUSSEN001 AS | Professional & scientific | 2011 |
| PNR Holding AS | Education | 2013 |
| Polaris Aviation AS | Transport & logistics | 2021 |
| Pontech Marina AS | Manufacturing | 2019 |
| Porta Eiendom AS | Real estate | 2021 |
| Porta Slemmestad AS | Real estate | 2014 |
| Portofino Herreklær AS | Wholesale & retail | 2012 |
| Pr-Utvikling AS | Real estate | 2023 |
| Praiser Group AS | Wholesale & retail | 2026 |
| Precision Milling AS | Manufacturing | 2020 |
| Pretex AS | Financial services | 2006 |
| Pretty Fast Promotions Ans | Education | 2009 |
| Pro-Bygg Home AS | Construction | 2022 |
| Prodoflex AS | Wholesale & retail | 2012 |
| Prodox Engineering AS | Professional & scientific | 1996 |
| Proffbygg AS | Construction | 2013 |
| Propex Gruppen Tønsberg AS | | 2025 |
| Protec Consult AS | Financial services | 2005 |
| Prove AS | Wholesale & retail | 2025 |
| Provento Partners AS | Health & social care | 2024 |
| PS Agenturer AS | Wholesale & retail | 2011 |
| PS Consulting AS | Health & social care | 2013 |
| Pssst AS | Professional & scientific | 2023 |
| Puls Inv AS | | 2025 |
| Pysix AS | Information & communication | 2022 |
| Pysix.Ai AS | Information & communication | 2025 |
| Qbic AS | Construction | 2003 |
| R-S Service AS | Transport & logistics | 2022 |
| Ragnarock AS | Administrative & support | 2015 |
| Raiga Bygg AS | Construction | 2019 |
| Ramdal Eiendom AS | Real estate | 2005 |