| NV Bygg & Entreprenad | Construction | 2010 |
| Ny Bolig Melhus AS | Construction | 2015 |
| Nye Sentu AS | | 2026 |
| Nygaard Kran & Transport AS | Transport & logistics | 2006 |
| Nylende Autosenter AS | Wholesale & retail | 2018 |
| O. L. Engen Eiendom AS | Real estate | 2007 |
| O.B.Wiik Covers AS | Administrative & support | 2023 |
| O.B.Wiik Hall AS | Wholesale & retail | 2023 |
| O.B.Wiik International AS | Administrative & support | 2023 |
| O.B.Wiik Services AS | Construction | 2023 |
| Oalon AS | Information & communication | 2025 |
| Obv Drift AS | Transport & logistics | 2018 |
| Oddis Holding AS | Financial services | 2018 |
| Odin Consulting AS | Professional & scientific | 2025 |
| Offar AS | | 2025 |
| Offroad Power AS | Administrative & support | 2010 |
| Ojr Rydland Holding AS | | 2022 |
| Oleka AS | Real estate | 2006 |
| Olinco AS | Financial services | 2017 |
| On Beach Invest AS | Financial services | 2007 |
| On Our Own Productions AS | Information & communication | 2015 |
| ONE2CEL AS | Wholesale & retail | 2010 |
| Onemed AS | Wholesale & retail | 1989 |
| Onemed Services AS | Transport & logistics | 2016 |
| Onninen AS | Wholesale & retail | 1998 |
| Opp Av Sjøen AS | Wholesale & retail | 2020 |
| Opplæringskontoret for Service Og Samferdsel SA | Education | 1994 |
| Optikk 2020 AS | Wholesale & retail | 2015 |
| Orkestra AS | Professional & scientific | 2018 |
| Oslo Auto Express AS | Other services | 2012 |
| Oslo Bilhjelp Holding AS | Real estate | 2015 |
| Oslo Bud & Vare AS | Transport & logistics | 2014 |
| Oslo Drift Og Vedlikehold AS | Construction | 2018 |
| Oslo Kjøl & Klima AS | Manufacturing | 2013 |
| Oslo Transport & Spedisjon AS | Transport & logistics | 2009 |
| Otman AS | Transport & logistics | 2021 |
| Otto Olsen AS | Wholesale & retail | 1998 |
| Otto Olsen Holding AS | Wholesale & retail | 2005 |
| Otto Olsen Invest AS | Real estate | 1990 |
| Ower Trafikkskole AS | Education | 2024 |
| Palfinger Norge AS | Wholesale & retail | 1999 |
| Palking AS | Professional & scientific | 2005 |
| Palking Eiendom AS | Real estate | 1997 |
| Pallesen Bygg AS | Construction | 2019 |
| Palrental AS | Administrative & support | 2023 |
| Pampedia AS | Professional & scientific | 2000 |
| Panda Sport AS | Wholesale & retail | 2018 |
| Panjabi Foods AS | Wholesale & retail | 2026 |
| Partner Elektro AS | Construction | 2022 |
| Partner-Invest AS | Real estate | 2022 |
| Partner.Eiendom AS | Real estate | 2022 |
| Pedersen's AS | Construction | 2018 |
| Pels Og Puls AS | Wholesale & retail | 2018 |
| Persontransfer AS | Transport & logistics | 2023 |
| Pesica Eiendom AS | Real estate | 1997 |
| Pesica Holding AS | Real estate | 2005 |
| Petite Frisørene Skedsmo Nuf | Other services | 2010 |
| Pettersen & Helgesen Bygg Og Tømrerservice AS | Construction | 1995 |
| Pharma Active AS | Real estate | 2008 |
| Pharmasense AS | Wholesale & retail | 2021 |
| Pill AS | | 2026 |
| Pilotmade AS | Information & communication | 2022 |
| Pitchpeak Group AS | Administrative & support | 2025 |
| Pizza Rivoluzione AS | Hospitality | 2021 |
| PKR & Miljø AS | Administrative & support | 2018 |
| Plaza AS | Real estate | 2025 |
| Plaza Event AS | Hospitality | 2016 |
| Plura Da | Wholesale & retail | 2025 |
| PMT Cargo Smartpoint Norway Nuf | Transport & logistics | 2019 |
| Pointec Nord AS | Information & communication | 1991 |
| Postlink AS | Wholesale & retail | 2015 |
| Potetbakeren Skedsmo Senter AS | Hospitality | 2026 |
| PR15A AS | Construction | 2025 |
| Practicemaster AS | Information & communication | 2021 |
| Premium Transport AS | Transport & logistics | 2026 |
| Presto AS | Construction | 1989 |
| Pro Gear Da | Information & communication | 1993 |
| Procon Digital AS | Information & communication | 2016 |
| Progressi AS | Professional & scientific | 2016 |
| Prosjektering AS | Construction | 2020 |
| Prosjektgruppen Norge AS | Construction | 2020 |
| Protrex AS | Manufacturing | 2021 |
| Provak Systemer AS | Wholesale & retail | 2016 |
| Psykologtjenester AS | Health & social care | 2023 |
| Punjab Engros AS | Wholesale & retail | 2026 |
| Putz Holding AS | | 2025 |
| Qbeecom AS | Information & communication | 2007 |
| QG Consulting AS | Information & communication | 2022 |
| Quickstep Invest AS | Real estate | 2018 |
| R Finans AS | | 2021 |
| R-Gruva AS | | 2023 |
| Rab Eiendom AS | Real estate | 2024 |
| Raimet Holding AS | | 2025 |
| Rasi AS | Wholesale & retail | 2017 |
| Raus Holding AS | Information & communication | 2019 |
| Ravegarden AS | Information & communication | 2012 |
| RAVN4 AS | | 2024 |
| RB Energi AS | Wholesale & retail | 2022 |
| RB Energi Holding 1 AS | | 2024 |
| RB Energi Holding 2 AS | | 2025 |