| Nære Invest AS | | 2019 |
| Nørd AS | Professional & scientific | 2017 |
| O Cofrinho AS | | 2025 |
| O Langseter & Sønn AS | Real estate | 1978 |
| O P Holding AS | Financial services | 2005 |
| Oal Invest AS | Real estate | 2005 |
| Ob Studio Produksjon AS | Information & communication | 1994 |
| Oceanobs AS | Professional & scientific | 2021 |
| Oddlien Holding AS | | 2021 |
| Oe Eiendomsinvest AS | Financial services | 2017 |
| Ohhs Holding AS | Health & social care | 2021 |
| Omsatt AS | Real estate | 2012 |
| Open Ocean Farming AS | Agriculture & fishing | 2020 |
| Open Ocean Holding AS | Manufacturing | 2020 |
| Opphold AS | Professional & scientific | 2020 |
| Opplæringskontoret for Små Håndverksfag SA | Education | 1997 |
| Opti Kompetanse AS | Education | 2022 |
| Optik & Synshjelp AS | Wholesale & retail | 1982 |
| Optisk Kompani Ski AS | Wholesale & retail | 2007 |
| Optometrist Mørch Gjerdingen AS | Wholesale & retail | 2026 |
| Organic Holding AS | Wholesale & retail | 2018 |
| Oslo Bil AS | Wholesale & retail | 2014 |
| Oslo Kammerakademi AS | Arts & recreation | 2019 |
| Oslo Monument AS | Manufacturing | 1985 |
| Oslo Monument Eiendom AS | Real estate | 2024 |
| Oslo Monument Holding AS | Real estate | 2024 |
| Oslo Prefab AS | Construction | 2019 |
| Oslo Rammedrift AS | Construction | 2005 |
| Oslo Sweater Shop AS | Wholesale & retail | 1974 |
| Oss Nordic AS | Professional & scientific | 2022 |
| Ota Studio AS | Professional & scientific | 2017 |
| Overvåkningseksperten AS | Construction | 2025 |
| Ovre Nordby Invest AS | | 2022 |
| P Østby Holding AS | Professional & scientific | 2025 |
| P. Westley Holdings AS | Other services | 2023 |
| Padden AS | | 2026 |
| Pagu Holding AS | Other services | 2016 |
| Panpharma Nordic AS | Wholesale & retail | 2017 |
| Pantronic AS | Wholesale & retail | 2007 |
| Parsa Språk- Og Kultursenter AS | Education | 2021 |
| Partum Invest AS | Financial services | 2017 |
| Pascal Automasjon Follo AS | Construction | 2021 |
| PASSION4FITNESS AS | Wholesale & retail | 2023 |
| Passiv Kapital AS | Information & communication | 2020 |
| Paulsbo Holding AS | Health & social care | 2024 |
| Pbob Holding AS | Wholesale & retail | 2021 |
| Pcdoktor AS | Wholesale & retail | 2007 |
| Pcu Company AS | Information & communication | 2015 |
| Pede Holding AS | | 2020 |
| Pedersen & Skogholt AS | Professional & scientific | 2004 |
| Pedersen & Skogholt Da | Professional & scientific | 1996 |
| Pedersen & Skogholt Holding AS | Professional & scientific | 2012 |
| Pedersen & Skogholt Regnskap AS | Professional & scientific | 2011 |
| Peli AS | Financial services | 2012 |
| Pelikan Investment AS | Administrative & support | 2003 |
| Pep Eiendom AS | Real estate | 2026 |
| Perio Forum AS | Health & social care | 1995 |
| Persistence AS | Information & communication | 2007 |
| Personlig Invest AS | | 2020 |
| Persson Investering AS | Financial services | 2018 |
| Pharmavax AS | Manufacturing | 2021 |
| Pharmavax Holding AS | Manufacturing | 2022 |
| PHN AS | | 2024 |
| Pifus AS | Information & communication | 2012 |
| Pimentel AS | Other services | 2019 |
| Pingsvin Invest AS | | 2025 |
| Pingvinen Familiebarnehage Da | Education | 1998 |
| Pixel Creation AS | Professional & scientific | 2024 |
| Pizza Italiano Ski AS | Hospitality | 2025 |
| PJ Holding AS | Financial services | 2017 |
| PLAN2HEALTH AS | Information & communication | 2023 |
| Pli Prosjekt AS | Professional & scientific | 2025 |
| Plts Investment & Logistics AS | Professional & scientific | 2023 |
| Poem AS | Manufacturing | 2005 |
| Pokeworld Ltd Nuf | Wholesale & retail | 2025 |
| Polaris Universal Language Institute AS | Education | 1993 |
| Popstars AS | Wholesale & retail | 2022 |
| Powerfeud AS | Professional & scientific | 2024 |
| Powertrain Europe AS | Manufacturing | 1992 |
| Ppe Eiendom AS | Real estate | 2018 |
| Pre Eiendom AS | Real estate | 2005 |
| Premium Bilsenter AS | Wholesale & retail | 2014 |
| Prestkampen Invest AS | | 2026 |
| Prestmåsan AS | Real estate | 2018 |
| Pri - Pedagogikk Rådgivning Innovasjon Da | Education | 2012 |
| Princess-Gruppen AS | Wholesale & retail | 1969 |
| Prismeta AS | Information & communication | 2020 |
| Pro Byggmester AS | Construction | 2025 |
| Pro Byggtjenester AS | Construction | 2021 |
| Production AS | Information & communication | 2026 |
| Proff Rør & Bygg AS | Construction | 2023 |
| Proff Tolk Norge AS | Professional & scientific | 2017 |
| Profutura AS | Arts & recreation | 2018 |
| Project Biker AS | Information & communication | 2017 |
| Proklean AS | Administrative & support | 2020 |
| Protegit AS | Administrative & support | 2021 |
| Proteseguiden AS | Education | 2026 |
| Proverbial Horse AS | | 2026 |
| Psykiater.No AS | Health & social care | 2025 |
| Psykolog Ermesjø AS | Health & social care | 2017 |