| Luftmateriell AS | Wholesale & retail | 1940 |
| Lugn AS | Real estate | 1993 |
| Lugn Hytter AS | Construction | 1983 |
| Lukas Bygg AS | Construction | 2013 |
| Luksusglans Renhold AS | Administrative & support | 2025 |
| Luli Eiendom AS | Real estate | 2018 |
| Lumimi AS | Wholesale & retail | 2020 |
| Lund Invest AS | Real estate | 2004 |
| Lunden Mek. AS | Other services | 2020 |
| Lunden Ventures AS | | 2020 |
| Lundquist Invest AS | Wholesale & retail | 2005 |
| Lunds Billakkering Glomstad AS | Other services | 2023 |
| Lungab AS | | 2023 |
| Luuna AS | Real estate | 2005 |
| LVT Holding AS | | 2021 |
| Lydkameratene AS | Administrative & support | 2019 |
| Lynex Flyttebyrå AS | Transport & logistics | 2025 |
| Lysebo Holding II AS | Wholesale & retail | 2011 |
| Lystad Eiendom AS | Manufacturing | 1986 |
| Lystad Spesialinnredninger AS | Manufacturing | 1986 |
| Lågen Eiendom AS | Real estate | 1997 |
| Låsesmeden Sandefjord AS | Administrative & support | 2000 |
| Læremiddelforlaget-Skagerrak Forlag AS | Information & communication | 2001 |
| Løb Invest Sandefjord AS | Construction | 2005 |
| Løbbedalen 17 AS | Real estate | 2016 |
| Løchen Fogth-Gården AS | Real estate | 2016 |
| Løft Opp AS | Professional & scientific | 2021 |
| Løkesisters AS | Education | 2013 |
| Løkka 8 AS | Real estate | 2012 |
| Løkka Bar Og Servering AS | Hospitality | 2025 |
| Løkka Barnehage Sandefjord AS | Education | 2015 |
| Løkka Holding AS | Financial services | 2017 |
| Løm Holding AS | | 2020 |
| Løndal AS | | 2023 |
| M & O Eiendom AS | Real estate | 2006 |
| M Nilsen Holding AS | | 2024 |
| M&B Design AS | Wholesale & retail | 2022 |
| M&M Håndverk Ans | Arts & recreation | 2023 |
| M-Tree AS | Wholesale & retail | 2024 |
| M.C. Holding AS | | 2025 |
| M.Haugen Invest AS | | 2024 |
| M.I.A. Holding AS | Professional & scientific | 2022 |
| M.K. Import AS | Wholesale & retail | 2018 |
| M.Svanberg AS | Construction | 2021 |
| M2 Kapital AS | | 2021 |
| M2 Sandefjord AS | Real estate | 2015 |
| M3E Holding AS | | 2024 |
| M4 Eiendom AS | Construction | 2016 |
| Ma Studio AS | Construction | 2014 |
| Ma-H Invest AS | Professional & scientific | 2023 |
| Macai AS | Information & communication | 2020 |
| Mace Holding AS | Financial services | 2005 |
| Macncarry AS | Information & communication | 2021 |
| Maddes AS | Other services | 2024 |
| Maestro Transport AS | Transport & logistics | 2011 |
| Magasinet Café AS | Hospitality | 2012 |
| Magdalen Holding AS | Wholesale & retail | 2015 |
| Magge AS | Financial services | 2020 |
| Maggish Invest AS | | 2024 |
| Magni Sports AS | Arts & recreation | 2017 |
| Magnus Larsen AS | Construction | 2012 |
| Magnus Oddenes Invest AS | Real estate | 2015 |
| Maha Invest AS | Information & communication | 2017 |
| Mainmove Living AS | Wholesale & retail | 2008 |
| Mainmove Sport AS | Wholesale & retail | 2012 |
| Maison Beauté AS | Other services | 2023 |
| Maka Group AS | | 2026 |
| Maki Norge AS | Wholesale & retail | 2016 |
| Malermester Gunnar CHR. Strøm AS | Construction | 2014 |
| Malermestrene Jensen AS | Construction | 1991 |
| Malme Eiendomsutvikling AS | Real estate | 2016 |
| Malwina I Adam | Construction | 2008 |
| Mamba Oscorp Holding AS | Real estate | 2023 |
| Mammaharmoni AS | Education | 2025 |
| Mammut Eiendom AS | Real estate | 2005 |
| Manka AS | | 2025 |
| Mannakorn AS | Arts & recreation | 2017 |
| Manpower Framnæs Installasjon AS | Administrative & support | 1975 |
| Manpower UK Limited | Administrative & support | 2006 |
| Mantra Beauty & Academy AS | Other services | 2017 |
| Marathon Sport Skogen & Co Ans | Wholesale & retail | 1986 |
| Maraton Invest AS | | 2020 |
| Marc L Eiendom AS | Wholesale & retail | 2021 |
| Marco Forvaltning AS | Professional & scientific | 1994 |
| Maremi Invest AS | Construction | 2007 |
| Mareno Holding AS | Financial services | 2005 |
| Marexconsult AS | Professional & scientific | 2020 |
| Marginata Holding AS | | 2021 |
| Maria Kelly Accounting AS | Professional & scientific | 2020 |
| Maria Kelly AS | Professional & scientific | 2015 |
| Marian AS | | 2006 |
| Mariannmar AS | Real estate | 2018 |
| Marine Installasjon AS | Administrative & support | 2003 |
| Marine Service AS | Manufacturing | 2010 |
| Marine Solution Holding AS | Financial services | 2010 |
| Marine Water Treatment AS | Wholesale & retail | 2015 |
| Marinho Aidar AS | | 2020 |
| Mario Holding AS | | 2023 |
| Marius O Eiendom AS | Administrative & support | 2012 |
| Marius O Holding AS | Administrative & support | 2012 |