| Marte Jervan AS | | 2023 |
| Martinsen Bil AS | Wholesale & retail | 2024 |
| MAS1 AS | Arts & recreation | 2015 |
| Mascot AS | Wholesale & retail | 1995 |
| Mascot Eiendom AS | Real estate | 1945 |
| Mascot Electronics AS | Wholesale & retail | 2002 |
| Maskin & Industriteknikk AS | Construction | 2010 |
| Matboden Fredrikstad AS | Hospitality | 2024 |
| Matrix Marine AS | Manufacturing | 2005 |
| Medthings AS | Professional & scientific | 2019 |
| Meggert Invest AS | Real estate | 2023 |
| Mehmeti Holding AS | | 2021 |
| Meløy Stokmarknes Eiendom AS | Real estate | 2012 |
| Mentor AS | Professional & scientific | 1998 |
| Menzi Muck Scandinavia AS | Wholesale & retail | 2017 |
| Merdem Holding AS | | 2026 |
| Mestr AS | Construction | 2026 |
| Meterra Tech AS | Professional & scientific | 2020 |
| MHL Invest AS | Real estate | 2018 |
| Michael Holst Murservice AS | Construction | 2018 |
| Miljøsentralen Øst AS | Wholesale & retail | 2024 |
| Mime Engineering AS | Professional & scientific | 2023 |
| Miss Blue Da | Arts & recreation | 2020 |
| Mistzone AS | Information & communication | 2022 |
| MKM & Sønner AS | Construction | 2013 |
| Moldøy Holding AS | Construction | 2024 |
| Montenor Gruppen AS | Administrative & support | 2021 |
| Moss Eldrehjelp & Eiendomsservice AS | Administrative & support | 2020 |
| Mosseveien 110 AS | Real estate | 1998 |
| Mossins Gate 9 AS | Real estate | 2023 |
| Motorsport Person Og Talentutvikling AS | Arts & recreation | 2022 |
| Mpe Eiendom AS | Real estate | 2026 |
| MSG AS | Financial services | 2005 |
| Mte-Bygg AS | Construction | 2025 |
| Munin AS | Information & communication | 1990 |
| Murmester Olav Hauge Eftf AS | Construction | 1989 |
| Myldrebu Invest AS | Professional & scientific | 2023 |
| Myre Øksnes Eiendom AS | Real estate | 2022 |
| Mærrapanna Hyttelag SA | Water & waste | 2001 |
| Mærrapanna Va-Foretak SA | Water & waste | 2010 |
| Møklegård Invest AS | | 2002 |
| Nabbetorpveien 106 AS | Real estate | 2023 |
| Naturbarna AS | Education | 2002 |
| Nautic Service AS | Wholesale & retail | 1985 |
| Nbs-Norges Brukthvitevare Service Ans | Wholesale & retail | 2002 |
| Nguyen Lerengen AS | Health & social care | 2024 |
| Nidhogg AS | Information & communication | 2016 |
| Niklas Eriksen Drift AS | Wholesale & retail | 2023 |
| Nimbus Group Øst AS | Wholesale & retail | 2021 |
| Nina AS | Wholesale & retail | 2010 |
| No Pain No Gain AS | Professional & scientific | 2016 |
| Nodig Eiendom AS | Real estate | 2006 |
| Nora Skauge AS | Wholesale & retail | 2023 |
| Nordli-Group AS | Financial services | 2016 |
| Noresca IT Consulting AS | Information & communication | 2025 |
| Norges Håndverker AS | Construction | 2021 |
| Normar Next AS | Professional & scientific | 2026 |
| Norpro AS | Professional & scientific | 1999 |
| Novus Fredrikstad Ans | Other services | 1988 |
| Nye Garn Og Gavestua Ans | | 1990 |
| Nye Lilleng Gård AS | Agriculture & fishing | 2008 |
| O. M. Klemsdal AS | Arts & recreation | 2013 |
| Ocw Bygg & Montasje AS | Construction | 2010 |
| Odin Composites Design and Engineering AS | Professional & scientific | 1991 |
| Odin Eiendomsdrift AS | Real estate | 2005 |
| Odin Eiendomsutvikling AS | Real estate | 2017 |
| Odin Elektro AS | Construction | 2015 |
| Odin Maskin AS | Manufacturing | 1984 |
| Odin Miljø AS | Construction | 2025 |
| Ohj Holding AS | | 2021 |
| Oksrød Hovedanlegg for Vann Og Avløp SA | Water & waste | 2012 |
| Oksrødkilen Vann- Og Avløpslag SA | Water & waste | 2011 |
| Oktavia AS | Construction | 2023 |
| Olisious Holdning AS | Manufacturing | 2024 |
| Omikron Elektro AS | Construction | 2004 |
| Onsøy Legesenter AS | Health & social care | 2001 |
| Onsøy Mur & Anlegg Eiendom Ans | Administrative & support | 1994 |
| Onsøy Regnskap AS | Professional & scientific | 2014 |
| Onsøy Reklame Og Tekstiltrykk Da | Manufacturing | 1995 |
| Onsøy Ridesenter - Stall HK AS | Arts & recreation | 2006 |
| Onsøy Rørleggerbedrift AS | Construction | 1985 |
| Onsøy Salg Og Leie AS | Real estate | 1997 |
| Onsøy Skjærgårdservice AS | Construction | 2017 |
| Onsøy Snø Og Utemiljø AS | Administrative & support | 2014 |
| Onsøy Synssenter AS | Wholesale & retail | 2019 |
| Onsøy Trafikkskole AS | Education | 2015 |
| Onsøyfjøset AS | Real estate | 2006 |
| Opas Kreditt AS | Administrative & support | 1995 |
| Ortega Invest AS | | 2024 |
| Osterøy K AS | Real estate | 2026 |
| Oxymera AS | Wholesale & retail | 2025 |
| Pancoveien 15 AS | Real estate | 2021 |
| Pancoveien 20 B AS | Real estate | 2021 |
| Pancoveien 22 a AS | Real estate | 2014 |
| Pancoveien 26 AS | Real estate | 2013 |
| Pancoveien 28 AS | Real estate | 1988 |
| Pancoveien 7 AS | Real estate | 2024 |
| Pancoveien 8 AS | Real estate | 2012 |
| Pancoveien Apotek AS | Wholesale & retail | 2024 |
| Pasira Holding AS | | 2023 |