| Maria Nila AS | Wholesale & retail | 2015 |
| Mariunor AS | | 2021 |
| Marius Design AS | Professional & scientific | 2010 |
| Masserud Utvikling AS | Real estate | 1989 |
| Mastil AS | Administrative & support | 2022 |
| Med Holding AS | | 2021 |
| Meddoc AS | Professional & scientific | 1999 |
| Mediagenten AS | Professional & scientific | 2016 |
| Medine Serin AS | | 2024 |
| Melby Auto Avdeling Skjetten AS | Other services | 2012 |
| Melby Drift Og Maskinutleie AS | Administrative & support | 2007 |
| Melbø Holding AS | | 2026 |
| Merdevegen 4C AS | Real estate | 2007 |
| Mesterverket AS | Real estate | 2024 |
| Metricworks AS | Information & communication | 2018 |
| MF Bygg AS | Construction | 2017 |
| Miami Dream AS | Transport & logistics | 2021 |
| Milestech AS | Information & communication | 2023 |
| Miljøisolasjon AS | Construction | 2024 |
| Mitro Norge AS | Construction | 2022 |
| MK Spedisjon AS | Transport & logistics | 2024 |
| Moaveien 31 AS | Real estate | 2007 |
| Mobile Repair Grønland AS | Other services | 2025 |
| Mosaic Solutions AS | Manufacturing | 2002 |
| Mover Systems No AS | Transport & logistics | 2020 |
| MRS VVS AS | Construction | 2016 |
| Munto AS | | 2024 |
| My Bakery AS | Manufacturing | 2004 |
| Mywifi Networks AS | Wholesale & retail | 1996 |
| Møller Bil Romerike AS | Wholesale & retail | 1992 |
| N2S Brands AS | Wholesale & retail | 2026 |
| NB Alta Nærvarme AS | Energy | 2018 |
| NB Klepp Nærvarme AS | Energy | 2026 |
| NB Årø Molde Nærvarme AS | Energy | 2026 |
| Nda Pollex AS | Construction | 2022 |
| Nergaard AS | Wholesale & retail | 2021 |
| Nerlis Holding AS | Other services | 2024 |
| Netto Holding AS | Real estate | 2019 |
| Nexus MK AS | Professional & scientific | 2018 |
| Nibe Regnskap AS | Professional & scientific | 2009 |
| Nor Fjell Invest AS | | 2020 |
| Nor Regnskap AS | Professional & scientific | 2023 |
| Norand Invest AS | | 2020 |
| Norbioen AS | Energy | 2024 |
| Nordbohus Romerike AS | Real estate | 2018 |
| Nordbohus Romerike Prosjekt AS | Real estate | 2021 |
| Nordic Auto Invest AS | Administrative & support | 2023 |
| Nordic-Bilhandel AS | Wholesale & retail | 2025 |
| Nordisk Energikontroll AS | Professional & scientific | 1996 |
| Norges Vel Drift AS | Real estate | 1997 |
| Norgesbooking AS | Real estate | 2013 |
| Norpot AS | Wholesale & retail | 2019 |
| Norsk Bruksgenbank SA | Transport & logistics | 2018 |
| Norsk Gullogsølvhandel AS | Wholesale & retail | 2024 |
| Norteko AS | Construction | 2012 |
| Norteko Fiber AS | Construction | 2020 |
| Norteko Utemiljø AS | Construction | 2020 |
| Nour Consulting AS | Professional & scientific | 2013 |
| Novema Aggregater AS | Manufacturing | 1967 |
| Nye Glocal View Eiendom AS | Real estate | 2020 |
| Nye Hytter AS | Manufacturing | 1998 |
| Nye Hytter Og Hus AS | Real estate | 2001 |
| Næringskraft AS | Energy | 2020 |
| Nært AS | Administrative & support | 1997 |
| Obo Bettermann AS | Wholesale & retail | 1976 |
| Ohjem AS | Professional & scientific | 2026 |
| Olaf Gjesti & Sønn AS | Wholesale & retail | 1986 |
| Olavsgaard Drift AS | Hospitality | 1989 |
| Olavsgaard Eiendom AS | Real estate | 1989 |
| Olavsgaard Gruppen AS | Hospitality | 1990 |
| Olavsgaard Hotell AS | Hospitality | 1985 |
| Olavsgaard Hotell Eiendom AS | Real estate | 1977 |
| Olavsgaard Kontorsenter AS | Real estate | 2016 |
| Olavsgaard Næringsbygg AS | Real estate | 1982 |
| Olavsgaard Næringspark AS | Real estate | 1999 |
| Omikron AS | Information & communication | 2019 |
| Onir Holding AS | Arts & recreation | 2005 |
| Opsahl & Osland Miljøkonsult Da | | 1989 |
| Optimal Bemanning AS | Health & social care | 2024 |
| Orogenic AS | Wholesale & retail | 2019 |
| Oslo Automatgear AS | Other services | 2012 |
| Oslo Høytrykksvask AS | Administrative & support | 2021 |
| Oslo Markise AS | Wholesale & retail | 2020 |
| Oslo Overflateteknikk AS | Construction | 2021 |
| Oslo Rides AS | Transport & logistics | 2022 |
| Oslo Viken Service AS | Construction | 2026 |
| Otto Olsen Boligutvikling AS | Financial services | 2016 |
| Otto Olsen Eiendom AS | Real estate | 1968 |
| Otto Olsen Skipsinvest AS | Transport & logistics | 1998 |
| P.M.A. Snekkerservice AS | Construction | 2024 |
| P.S. Bygg AS | Construction | 2020 |
| Pacha AS | Wholesale & retail | 2017 |
| Panser AS | Wholesale & retail | 1995 |
| Parkett Design AS | Construction | 2021 |
| Pcsb-Co AS | Professional & scientific | 2015 |
| Peducon Nagel Og Larsen Pedagogisk Og Økonomisk Rådgivning Ans | Administrative & support | 1987 |
| Pemasol Oslo Nord AS | Construction | 2025 |
| Per Erik Lerseth AS | Financial services | 2005 |
| Persand AS | Construction | 2007 |
| Peti AS | Wholesale & retail | 2017 |