| Lille Bohem AS | Wholesale & retail | 2017 |
| Lille Åsgård AS | Real estate | 2019 |
| Lillelia Gårdsbarnehage AS | Education | 2007 |
| Lime-Invest AS | | 2021 |
| Lindekilde AS | | 2024 |
| Lindo AS | Hospitality | 2016 |
| Line Solgaard Arkitekter AS | Professional & scientific | 2022 |
| Line Solgaard AS | Professional & scientific | 2022 |
| Link Boligutleie Østfold AS | Real estate | 2023 |
| Linspire.No AS | Wholesale & retail | 2018 |
| Lise Bøckmann Olsen AS | Financial services | 2013 |
| Lisleby Flyttebyrå AS | Transport & logistics | 1996 |
| Lislebyveien 52 AS | Real estate | 1979 |
| Lislebyveien 58 AS | Real estate | 2003 |
| Listranda Syd Vann Og Avløp SA | Water & waste | 2017 |
| Listverkfabrikken Fjeldberg Bruk AS | Wholesale & retail | 2003 |
| Liveshow AS | Administrative & support | 2023 |
| Livsstil Holding AS | Wholesale & retail | 2005 |
| Lma Holding AS | | 2023 |
| Lokalet F13 AS | Hospitality | 2024 |
| Lonkan Medisinske AS | Health & social care | 2017 |
| Loonie Marketing Da | Professional & scientific | 2023 |
| Los Tacos Fredrikstad AS | Hospitality | 2017 |
| Losen Hvaler AS | Hospitality | 2021 |
| Losjeveien 2 AS | Real estate | 2016 |
| Louise Invest AS | Financial services | 2009 |
| Loxen Capital AS | | 2026 |
| LS Totalservice AS | Administrative & support | 2026 |
| Ludmila Victoria Andersen AS | Health & social care | 2016 |
| Luftteknikk AS | Construction | 2010 |
| Luka Eiendom AS | Real estate | 2014 |
| Lule Invest AS | | 2023 |
| Luma Øst AS | Professional & scientific | 2014 |
| Lundestadtoppen 2 AS | Real estate | 2016 |
| Lush Festivalen AS | Arts & recreation | 2026 |
| Luxe-Anette Bakkers Frisør & Makeup Studio AS | Other services | 2012 |
| Lykkeberg Eiendom AS | Real estate | 1993 |
| Lykkeberg Holding AS | Real estate | 2004 |
| Lykkeberg Hotell Eiendom AS | Real estate | 2004 |
| Lykkeberg Næringseiendom AS | Real estate | 2004 |
| Lykkeberg Parkering AS | Real estate | 2004 |
| Lægene På Kirkebrygga Da | Health & social care | 2014 |
| Løpsklinikken Fredrikstad AS | Wholesale & retail | 2010 |
| M Cafè AS | Hospitality | 2011 |
| M.A Hodl AS | Real estate | 2022 |
| M.O.S Holding AS | | 2021 |
| M2 Redesign AS | Administrative & support | 2022 |
| Ma Wei AS | Wholesale & retail | 2024 |
| Ma-Jo Holding AS | Financial services | 2009 |
| Made in Fredrikstad AS | Arts & recreation | 2017 |
| Madison Invest AS | Financial services | 1998 |
| Mads Gjølberg Holding AS | | 2018 |
| Magne Aardalen AS | Construction | 2022 |
| Magnus Ekeberg AS | | 2019 |
| Magnussons Holding AS | Construction | 2021 |
| Mainframe Data AS | Information & communication | 2001 |
| Majemo Holding AS | | 2026 |
| Majemo Invest AS | Professional & scientific | 2023 |
| Malerfirma Hans Kjøstelsen AS | Construction | 2012 |
| Malermester Buer Østfold AS | Construction | 2019 |
| Malin Meland AS | Other services | 2024 |
| Malin Røsstad Invest AS | | 2022 |
| Malleo Holding AS | Wholesale & retail | 2019 |
| Malm Design AS | Professional & scientific | 2022 |
| Malys AS | Professional & scientific | 2018 |
| Mama Cicignon AS | Real estate | 2025 |
| Mange Muligheter AS | Other services | 2015 |
| Manstad Kjøtt Eiendom AS | Real estate | 2007 |
| Manstad Utvikling AS | Real estate | 2008 |
| Marcato Da | Arts & recreation | 1994 |
| Marcus Ogre Holding AS | Real estate | 2014 |
| Mariann Eiendom AS | Real estate | 2005 |
| Maritech Engineering AS | Professional & scientific | 2012 |
| Marstal AS | Real estate | 2013 |
| Martin Tveit Holding AS | | 2025 |
| Martine Lier AS | Arts & recreation | 2025 |
| Martinsen & Sønn Eiendom AS | Real estate | 2005 |
| Martinsen & Sønn Installasjon AS | Construction | 2009 |
| Martinsen Og Sønn Elektro AS | Wholesale & retail | 2003 |
| Maskin Trading AS | Wholesale & retail | 2024 |
| Mathis Holding AS | Real estate | 2022 |
| Matlok Holding AS | | 2023 |
| Mattis Snekkertjeneste AS | Construction | 2011 |
| Maverick Interiørarkitekter AS | Professional & scientific | 2021 |
| Maxim Invest AS | Real estate | 2007 |
| MCN Invest AS | Real estate | 2006 |
| Meat Services AS | Information & communication | 2007 |
| Medi Partner AS | Wholesale & retail | 1992 |
| Medi Partner Holding AS | Wholesale & retail | 2005 |
| Mediator AS | Professional & scientific | 2001 |
| Medice Nordic Norway AS | Wholesale & retail | 2015 |
| Medicue AS | Information & communication | 2021 |
| Medicus AS | Health & social care | 2003 |
| Medisinsk Senter for Overvekt Og Forskning AS | Professional & scientific | 1993 |
| Medtech Innovation Cluster AS | Professional & scientific | 2024 |
| Meidellkraft AS | Information & communication | 2019 |
| Mentellow AS | Wholesale & retail | 2017 |
| Mentor Consulting AS | Professional & scientific | 2012 |
| Mereo Invest AS | Real estate | 2022 |
| Meridian Nordic Ltd Nuf | Administrative & support | 2006 |