| Levykauppa 33 RPM Oy | Wholesale & retail | 2020 |
| Licence to learn Ltd | Education | 2016 |
| Liikennekoulu Pentti Männistö Ky | Education | 1979 |
| Liikenneopetus Simox Oy | Education | 2012 |
| Liikuntapalvelut LiikeVoima Oy | Arts & recreation | 2014 |
| Lillin Talli Oy | Agriculture & fishing | 2014 |
| Limet Oy | Administrative & support | 2019 |
| Lindell Flowers Chainsales Oy Ab | Wholesale & retail | 2012 |
| Lindell Flowers Shop Oy Ab | Wholesale & retail | 2012 |
| Linnus-Auto Oy | Other services | 1979 |
| Lion Partners Oy | Administrative & support | 2019 |
| Livion Oy | Information & communication | 2011 |
| Log Cent Oy | Transport & logistics | 2005 |
| Logitas Oy | Professional & scientific | 1996 |
| Logopen Finland Oy | Wholesale & retail | 2009 |
| Lohtajan energiaosuuskunta | Agriculture & fishing | 2001 |
| Loistoasunnot Oy | Real estate | 2019 |
| Lomasalonen Oy | Real estate | 1976 |
| Lounaskahvila Harald Oy | Hospitality | 2019 |
| Lounaskahvila Minna Oy | Hospitality | 2002 |
| Low Energy Finland Oy | Construction | 2019 |
| Lucas Hägglund Oy | Manufacturing | 2024 |
| Lukkorautaset Oy | Wholesale & retail | 1989 |
| Lumimies Oy | Financial services | 2022 |
| Lumiparvi Oy | Transport & logistics | 2024 |
| Luokkahitsauspalvelu Hannu Lund Oy | Professional & scientific | 1994 |
| Luottokone oy | Other services | 2019 |
| Lvi-Rapi Oy | Construction | 2009 |
| Lynovia Oy | Arts & recreation | 2017 |
| Länsi-Suomen Putki Ja Sähkötekijät OY | Construction | 2011 |
| Länsirannikon Arvokiinteistöt OY | Real estate | 2010 |
| LähiFysio Oy | Health & social care | 2018 |
| Lämpö-Expert Ky | Construction | 1985 |
| Lämpöpartio Kiinteistöt Oy | Construction | 2012 |
| Lämpöpartio Oy | Construction | 2011 |
| Länsi-Suomen Porakaivo Oy | Construction | 2007 |
| Länsirannikon Biljardi Oy | Hospitality | 1992 |
| Länsirannikon Osuuspankki | Financial services | 1928 |
| M & J Kiviniemi Oy | Wholesale & retail | 2014 |
| M & P Kone Ky | Manufacturing | 1986 |
| M Force Oy | Professional & scientific | 2022 |
| M Laxström Oy Ab | Wholesale & retail | 2021 |
| M&M Sorvisto Trading Oy | Wholesale & retail | 2015 |
| M.A. Slotte & C:o | Wholesale & retail | 1922 |
| M.Essel Oy | Professional & scientific | 2020 |
| MAHTT-Invest Oy | Financial services | 2021 |
| MAP Trade Oy | Wholesale & retail | 2003 |
| MARACS Oy | Professional & scientific | 2024 |
| MHK Works Oy | Transport & logistics | 2022 |
| MK-Sijoitus Oy | Financial services | 2009 |
| ML Kone ja vuokraus Oy | Transport & logistics | 2014 |
| MM Rakennus Tech Oy | Construction | 2022 |
| MMI Company Ab Oy | Manufacturing | 2018 |
| MNP Capital Oy | Real estate | 2021 |
| MS Uniikkikodit Oy | Real estate | 2023 |
| MT Beata Oy | Hospitality | 2010 |
| MT Invest Oy Ab | Real estate | 2021 |
| MVR Y-Kone Oy | Construction | 2024 |
| Maa- ja Tierakennus Myllykoski Oy | Construction | 2003 |
| MaaN Holding Oy | Professional & scientific | 2024 |
| Maalauspalvelu Tuomaala Oy | Construction | 2013 |
| Maalerei Oy | Construction | 1994 |
| Maanrakennus B. Dahlbacka Oy | Construction | 1984 |
| Maanrakennus Janne Peltola Oy | Construction | 2019 |
| Maanrakennus KoneKari Oy | Construction | 2008 |
| Maanrakennus Salmi Oy | Construction | 1990 |
| Maanrakennus T.Meriläinen Oy | Construction | 2020 |
| Maansiirto JR Oy | Construction | 2022 |
| Maansiirto U Tuominiemi Oy | Construction | 1981 |
| Madez Lounge Oy | Hospitality | 2023 |
| Madez avoin yhtiö | Hospitality | 2021 |
| Madi Medical Oy | Health & social care | 2025 |
| Magnus Company Oy Ab | Real estate | 2019 |
| Mainio Kukkakauppa Oy | Wholesale & retail | 2026 |
| Mainos-Kepari Ky | Professional & scientific | 1987 |
| Majani Oy | Wholesale & retail | 2020 |
| Majapaikka Oy | Real estate | 2025 |
| Majatalo Pormestari Oy | Hospitality | 2026 |
| Malvest Oy | Administrative & support | 2016 |
| Mammun Hyväkakku Oy | Manufacturing | 2018 |
| Mantex Oy | Administrative & support | 2005 |
| Mapnex Oy | Wholesale & retail | 1995 |
| MarMir Oy | Administrative & support | 2022 |
| Maracon Infra Oy | Construction | 2021 |
| Marc Svahn Oy | Wholesale & retail | 1997 |
| Marjan Invest Oy | Financial services | 2025 |
| Marjatta Tiittasen Grillit kommandiittiyhtiö | Hospitality | 1991 |
| Markens Kraft Ab | Professional & scientific | 2023 |
| Marketing & Communication Group Marco Oy | Administrative & support | 2017 |
| Markkinointi Ha-Mi Ky | Wholesale & retail | 1985 |
| Markkinointi Juha Kivinen Oy | Professional & scientific | 1989 |
| Mary's La Favorita Oy | Hospitality | 1987 |
| Masac Oy | Administrative & support | 2006 |
| Masan Milli OY | Construction | 2013 |
| MaskControl Oy | Professional & scientific | 2026 |
| Maslotec Oy | Construction | 2008 |
| Matildas Café 2 Ab | Hospitality | 2012 |
| Matka-Vesa Vesa Hirsikangas Ky | Administrative & support | 1995 |
| Mattias Ahola Ab | Administrative & support | 2020 |
| Mattila Ky Jouko Mattila | Construction | 1983 |