| Oewa AS | Professional & scientific | 2015 |
| Officedesk AS | Professional & scientific | 2018 |
| Ofk Holding AS | Financial services | 2005 |
| Ogvind AS | Energy | 2022 |
| Ohantho Holding AS | Administrative & support | 2017 |
| Ohm Bjellands Rederi AS | Professional & scientific | 2017 |
| Oiks Holding AS | Construction | 2018 |
| Okbu Opplæringskontor Barne Og Ungdomsarbeiderfag SA | Education | 2016 |
| Oktagon AS | Manufacturing | 2019 |
| Olav Den Hellige AS | Energy | 2021 |
| Olav Knutsen AS | Professional & scientific | 1960 |
| Olav Sæbø Handel AS | Real estate | 1993 |
| Old Bridge AS | Wholesale & retail | 2020 |
| Ole Sande AS | | 2019 |
| Ole Vikre AS | Wholesale & retail | 2021 |
| Olga Haugesund AS | Wholesale & retail | 2007 |
| Oli Knowledge AS | Financial services | 2007 |
| Olsen Og Nygaard AS | Real estate | 2007 |
| Oluf Holding AS | | 2025 |
| Omega Takst AS | Real estate | 2019 |
| Omf Holding AS | | 2005 |
| Omnia Helsebygg AS | | 2016 |
| Ona Fus Barnehage AS | Education | 2024 |
| Opp AS | Professional & scientific | 2021 |
| Oppetveiten Tomt AS | Real estate | 2023 |
| Oppgjørspartner AS | Real estate | 2010 |
| Optiker Hedegaard AS | Wholesale & retail | 1988 |
| Opus Arkitekter Holding AS | Professional & scientific | 2008 |
| Orplid AS | Financial services | 2023 |
| Orshaugen 22 AS | Real estate | 2012 |
| Osa Bygg & Eiendom AS | Construction | 2024 |
| OSS2 AS | Wholesale & retail | 2020 |
| Otech Group AS | Manufacturing | 2016 |
| Otech Invest AS | Manufacturing | 2011 |
| Otiv Invest AS | Real estate | 1987 |
| Otto Amundsen AS | Real estate | 1932 |
| Otv Invest AS | | 2022 |
| Oud AS | Hospitality | 2023 |
| Ove Skarven AS | Financial services | 2016 |
| Ovemco AS | | 2022 |
| Overslag AS | | 2018 |
| Owner AS | Information & communication | 2022 |
| P Invest AS | | 2012 |
| P.Kolbjørnsen AS | Manufacturing | 2025 |
| P/R Olav Østensjø JR. Ans | Transport & logistics | 1987 |
| Palident AS | Manufacturing | 2019 |
| Paloma Holding AS | Real estate | 2005 |
| Paloma Holding II AS | Real estate | 2021 |
| Pappask Invest AS | Financial services | 2023 |
| Parcon AS | Real estate | 2020 |
| Paris Frisør Silas AS | Other services | 2015 |
| Park Terrasse AS | Real estate | 1985 |
| Parkteateret Utvikling AS | Real estate | 2019 |
| Parthenon AS | Real estate | 2002 |
| Partner Invest AS | Hospitality | 1998 |
| Partrederiet Vea & Vea Da | Agriculture & fishing | 1995 |
| Paxon AS | Professional & scientific | 2019 |
| Paytec AS | Professional & scientific | 2012 |
| PC Verkstedet AS | Other services | 2012 |
| Peaklab AS | Education | 2026 |
| Pedersen Agentur Norge AS | Administrative & support | 2016 |
| Pelina AS | Professional & scientific | 2024 |
| Pensel Maling & Design AS | Construction | 2018 |
| Per Velde AS | Wholesale & retail | 1974 |
| Per Velde Eiendom AS | | 2005 |
| Per Velde Eiendom II AS | Real estate | 2007 |
| Perdi Holding AS | | 2025 |
| Perleporten Vest AS | Wholesale & retail | 2016 |
| Permanor AS | Manufacturing | 1998 |
| Permanor Brumunddal AS | Manufacturing | 2016 |
| Person Til Person AS | Other services | 2024 |
| Perspektiv Film & Foto AS | Information & communication | 2015 |
| Persson Elektro AS | Construction | 1984 |
| Persson Elektro Eiendom AS | Real estate | 1946 |
| Pesukaru Invest AS | | 2025 |
| Petra Solid AS | | 2023 |
| Petrock II AS | Real estate | 2011 |
| Petter Steen Consulting AS | Education | 2015 |
| Petters Holding AS | Financial services | 2005 |
| Pfita AS | Arts & recreation | 2024 |
| Pge Invest AS | Real estate | 2005 |
| Piibaa AS | Professional & scientific | 2026 |
| Pili Invest AS | Real estate | 2005 |
| Pioneer AS | | 2025 |
| Pipespesialisten Da | Wholesale & retail | 1999 |
| Pitterskafè AS | Hospitality | 2007 |
| PJR Invest AS | | 2005 |
| Plan B Gate AS | Hospitality | 2019 |
| Pleieriet AS | Other services | 2017 |
| Plen Holding AS | Financial services | 2017 |
| Plethora AS | | 2015 |
| Pling Holding AS | | 2022 |
| Pluss-Eiendom AS | Real estate | 2018 |
| PME123 AS | Professional & scientific | 2021 |
| Pmo Invest AS | Financial services | 2009 |
| Poker Travels AS | Administrative & support | 2024 |
| Poppcorn Design AS | Professional & scientific | 2020 |
| Porshaug Eiendom AS | Real estate | 2019 |
| Port Eiendom AS | Real estate | 2009 |
| Praktips AS | Professional & scientific | 2017 |