| Lørenparken Parkering AS | Real estate | 2013 |
| Lørenskog Sentrum Bolig AS | Real estate | 2008 |
| Løven Transport AS | Transport & logistics | 2024 |
| Løvenstad Utvikling AS | Real estate | 2021 |
| Løvgreen AS | Construction | 2017 |
| M Fjeldberg Holding AS | | 2025 |
| M Skaug Holding AS | | 2025 |
| M Studio Frisør&Skjønnhet AS | Other services | 2024 |
| M Sund AS | Transport & logistics | 2001 |
| M&K Ellingsen AS | | 2022 |
| M&S Eiendom AS | Real estate | 2023 |
| M.E.N.S AS | Administrative & support | 2025 |
| Maco Invest AS | Wholesale & retail | 2005 |
| Magic Lillestrøm AS | Other services | 1990 |
| Magnus Skjønhaug Invest AS | Financial services | 2016 |
| Making Place AS | Transport & logistics | 2023 |
| Makithos Holding AS | | 2023 |
| Malandro AS | Information & communication | 2025 |
| Maler Fix AS | Construction | 2019 |
| Maler På Hjul AS | Wholesale & retail | 2024 |
| Malviken AS | Real estate | 2022 |
| Malviken Malermester AS | Construction | 2021 |
| Mana VVS AS | Construction | 2023 |
| Maol AS | Professional & scientific | 2022 |
| Marathon Solutions AS | Professional & scientific | 2024 |
| Marel Norge AS | Wholesale & retail | 1921 |
| Marfor Invest AS | Financial services | 2012 |
| Marias Holding AS | | 2020 |
| Marienfryd Eiendom AS | Real estate | 2014 |
| Marikollen Eiendom AS | Real estate | 2020 |
| Marine Tech AS | Construction | 2003 |
| Marini Consulting AS | Professional & scientific | 2023 |
| Marius Strandhaug AS | | 2024 |
| Marte Dreier Audiopedagog AS | Education | 2018 |
| Martin K Holding AS | Construction | 2024 |
| Martin's Eiendom AS | Real estate | 2005 |
| Martins AS | Hospitality | 2005 |
| Martins Bingo AS | Arts & recreation | 2011 |
| Martins Lillestrøm AS | Hospitality | 2018 |
| Maruey Thai-Mat Take Away Og Catering AS | Hospitality | 2017 |
| Mats & Janne AS | Hospitality | 2017 |
| Matsaya Group AS | Hospitality | 2026 |
| Matssen Invest AS | Financial services | 2013 |
| Matstasjon Ans | Wholesale & retail | 2003 |
| Maxima Mote Lillestrøm AS | Wholesale & retail | 2012 |
| Mediafy Relations AS | Information & communication | 2022 |
| Meera AS | | 2023 |
| Megabad AS | Construction | 2023 |
| Megacasa AS | Wholesale & retail | 2025 |
| Megapiksel AS | Information & communication | 2021 |
| Meglerprint AS | Professional & scientific | 2017 |
| Meierikvartalet Næring AS | Real estate | 2025 |
| Meierikvartalet Utleie AS | Real estate | 2023 |
| Mel Gardermoen 14 AS | Real estate | 2021 |
| Mel Heia 1 AS | Real estate | 2022 |
| Mel Heia 19 AS | Real estate | 2022 |
| Mel Heia 20 AS | Real estate | 2022 |
| Mel Heia 22 AS | Real estate | 2022 |
| Melby Auto Avd Lillestrøm AS | Other services | 2009 |
| Melgårdshagan 57-63 Holding AS | | 2025 |
| Mellan Öronen AB Nuf | Health & social care | 2024 |
| Menko Undervisning AS | Education | 2015 |
| Mentoria AS | Professional & scientific | 2001 |
| Mentoria Holding AS | Professional & scientific | 2019 |
| Mercurius Invest AS | Real estate | 1997 |
| Mesfin Consulting AS | Professional & scientific | 2026 |
| Messehallen Elektriske AS | Construction | 1966 |
| Mesterlys AS | Administrative & support | 1994 |
| MGV Invest AS | | 2025 |
| Mias Lykkeland AS | | 2023 |
| Midt Næring AS | Real estate | 2019 |
| Miinto.No AS | Information & communication | 2010 |
| Mikheim AS | Professional & scientific | 2019 |
| Miljøvakta AS | Professional & scientific | 2011 |
| Min Blikkenslager AS | Construction | 2021 |
| Min Jordmor Da | Health & social care | 2013 |
| Min Programvare AS | Information & communication | 1996 |
| Mine Krefter AS | Arts & recreation | 2025 |
| Minuttburger AS | Hospitality | 2004 |
| Mira Byggeprodukter Norge AS | Wholesale & retail | 2001 |
| Mirax Holding AS | Real estate | 2012 |
| Mirror Pictures Da | Information & communication | 2005 |
| Mkopperud Holding AS | | 2024 |
| MM Eiendomsinvest AS | Real estate | 2025 |
| Moab AS | Arts & recreation | 2025 |
| Mobcoder AS | Information & communication | 2024 |
| Moberghaugen Invest AS | Professional & scientific | 2020 |
| Modus I AS | Professional & scientific | 2023 |
| Modus X AS | Professional & scientific | 2023 |
| Moe Holding AS | Real estate | 2005 |
| Moguntia AS | Wholesale & retail | 2012 |
| Monit AS | Information & communication | 2022 |
| Monteroza AS | Professional & scientific | 2015 |
| Monteroza Consult & Invest AS | Professional & scientific | 2019 |
| Morten a Larsen AS | | 2025 |
| Morten Dahle Holding AS | Real estate | 2008 |
| Morten Ringstad Holding AS | Real estate | 2021 |
| Mostue Lillestrøm AS | Wholesale & retail | 2001 |
| Motion Media AS | Professional & scientific | 2024 |
| Motor Bil Rekvisita AS | Wholesale & retail | 1989 |