| Maskin Og Truckopplæring AS | Education | 2014 |
| Masters AS | Arts & recreation | 2023 |
| Matsjefen AS | Wholesale & retail | 2026 |
| Mauser-Noreko AS | Water & waste | 1996 |
| Mbes - Moss Bygg Og Eiendomsservice AS | Professional & scientific | 2020 |
| MBM Eiendom AS | Real estate | 2007 |
| Me & Wilma AS | Wholesale & retail | 2018 |
| Mechanical Support AS | Professional & scientific | 2006 |
| Medco AS | Manufacturing | 2001 |
| Mediamontasje AS | Professional & scientific | 2023 |
| Mediasus AS | Wholesale & retail | 2022 |
| Medicus Eiendom Moss AS | Real estate | 2009 |
| Mediskin Solution AS | Wholesale & retail | 2025 |
| Medix Førstehjelp AS | Health & social care | 2019 |
| Medizone AS | Manufacturing | 2023 |
| Meglergaarden AS | Real estate | 2004 |
| Mei AS | Real estate | 2023 |
| Meili Bidco AS | Energy | 2020 |
| Meili Midco AS | Energy | 2020 |
| Meili Topco AS | Energy | 2020 |
| Mekaniker'N Jonny AS | Manufacturing | 2009 |
| Mekatronikk Holding AS | Real estate | 2005 |
| Mellers Hus AS | Wholesale & retail | 2020 |
| Melløs Apotek AS | Wholesale & retail | 2024 |
| Melløsparken Barnehage SA | Education | 2001 |
| Memento Consult AS | Professional & scientific | 2015 |
| Mereffekt AS | Professional & scientific | 2003 |
| Merking Og Sikring AS | Real estate | 1989 |
| Merlot AS | Real estate | 2005 |
| Merrick AS | Professional & scientific | 2016 |
| Mesa-Eiendom AS | Real estate | 2018 |
| Mesitech AS | Professional & scientific | 2024 |
| Mesterarkitekt AS | Professional & scientific | 2024 |
| Mesterbygg Moss AS | Construction | 2007 |
| Metabygg AS | Administrative & support | 2011 |
| Metaleco AS | Wholesale & retail | 2013 |
| Metho AS | Information & communication | 2015 |
| Metra Næringsmegling AS | Real estate | 2003 |
| Meyer Drift AS | Professional & scientific | 2020 |
| MG Eiendom Ans | Real estate | 2004 |
| MHM Artist AS | Arts & recreation | 2013 |
| Mhtech AS | Professional & scientific | 2016 |
| Microinvest Norge AS | Construction | 2023 |
| Micronova AS | Wholesale & retail | 2003 |
| Mida AS | Real estate | 1997 |
| Mida Holding AS | Real estate | 1997 |
| Midtlyng Invest AS | Education | 2021 |
| Midtre Maano Invest AS | | 2025 |
| Mih AS | Wholesale & retail | 2020 |
| Miin Helse AS | Health & social care | 2014 |
| Mikarlsen-Bygg Ans | Professional & scientific | 1995 |
| Mikhaf Invest AS | | 2018 |
| Mikro Elektroservice AS | Construction | 2018 |
| Mikrohus for Alle AS | Real estate | 2022 |
| Mila Noire AS | Manufacturing | 2025 |
| Miljø & Kvalitet Holding AS | Administrative & support | 2020 |
| Mill Telecom Invest AS | Information & communication | 2011 |
| Mim Holding AS | | 2021 |
| Mind Eiendom AS | Real estate | 2020 |
| Mind Holding AS | Real estate | 2005 |
| Mini-Import AS | Wholesale & retail | 2019 |
| Minna DK AS | Other services | 2015 |
| Mio Solitun Seniorpensjonat AS | Real estate | 2018 |
| Miri AS | Transport & logistics | 2023 |
| Mis - Moss Isolasjonsservice AS | Construction | 2000 |
| Missingmyrveien 78-80 AS | Real estate | 2025 |
| Mister Fix AS | Other services | 2020 |
| Mit Eiendom AS | Real estate | 2019 |
| Mitt Norske AS | Wholesale & retail | 2020 |
| Miwas AS | Administrative & support | 2022 |
| MJC AS | Administrative & support | 2020 |
| MK Bilsenter AS | Wholesale & retail | 2024 |
| MK Service Spolka Jawna | Administrative & support | 2020 |
| ML Eiendomsforvaltning AS | Real estate | 2021 |
| MLS AS | Manufacturing | 2020 |
| Mo-Invest AS | Real estate | 2020 |
| Moba Bedriftsutvikling AS | Professional & scientific | 2016 |
| Mobi AS | Real estate | 1998 |
| Mobil Antirust AS | Other services | 2022 |
| Mobile Moss AS | Other services | 1982 |
| Mobo AS | Real estate | 2022 |
| Moderne Formverksted AS | Manufacturing | 1985 |
| Modi Kaffe AS | Hospitality | 2025 |
| Modulex Norge AS | Wholesale & retail | 1980 |
| Moe-Consulting AS | Professional & scientific | 2022 |
| Moj Eiendom AS | Real estate | 2019 |
| Moj Maskin AS | Administrative & support | 2019 |
| Mok Eiendom 4 AS | Real estate | 2005 |
| Mok Eiendom AS | Real estate | 2018 |
| Mok Holding AS | Manufacturing | 2018 |
| Molea AS | Wholesale & retail | 2012 |
| Moleculart AS | Wholesale & retail | 2026 |
| Mona & Sissi AS | Wholesale & retail | 2021 |
| Monamors Håndarbeider AS | Manufacturing | 2022 |
| Monge Eiendom AS | Real estate | 1995 |
| Monge Frisør AS | Other services | 2013 |
| Montana Invest 1 AS | Real estate | 2006 |
| Montanus Konsult AS | Financial services | 2014 |
| Monteringspesialisten AS | Transport & logistics | 2024 |
| Moody Holding AS | | 2021 |