| Loppu Aarre Oy | Financial services | 2026 |
| Louhi Holding Oy | Financial services | 2012 |
| Louhintavalkonen Ky | Construction | 1984 |
| Love Mojo Brewing Oy | Manufacturing | 2025 |
| Luhangan Lämpö Oy | Energy | 1995 |
| Lukkokeskus Harri Manninen Ky | Wholesale & retail | 1989 |
| Lumieli Oy | Health & social care | 2021 |
| Lumio Events Oy | Arts & recreation | 2018 |
| Lumme Energia Oy | Energy | 2006 |
| Luna Living Oy | Manufacturing | 2024 |
| Luomanto Oy | Administrative & support | 2014 |
| Luontaistuote Päivänpaiste Ky | Wholesale & retail | 1996 |
| Luovahovi Oy | Health & social care | 2017 |
| Lupaava Oy | Construction | 2022 |
| Lux visibilis Oy | Health & social care | 2023 |
| LuxJewelle Oy | Wholesale & retail | 2022 |
| LuxSaimaa Oy | Construction | 2021 |
| Luxhammar Oy | Wholesale & retail | 1998 |
| Luxor Kiinteistöt Oy | Real estate | 2020 |
| LähiTapiola Savo-Karjala Keskinäinen Vakuutusyhtiö | Financial services | 1937 |
| Lämmin taksi Oy | Transport & logistics | 2023 |
| Lämpökulma Oy | Construction | 2019 |
| Länsi-Savo Oy | Real estate | 2012 |
| Länstuul Ky | Hospitality | 2004 |
| Läpivirtaus Oy | Transport & logistics | 2020 |
| Lääkäripalvelut Sipponen Oy | Health & social care | 2025 |
| Lääkärit Siiskonen Oy | Health & social care | 2020 |
| M&A Trading Oy | Wholesale & retail | 2021 |
| M-Logistics Oy | Wholesale & retail | 2006 |
| M. Mokki Ky | Wholesale & retail | 2011 |
| M.A.T.-Yritys Oy | Financial services | 1989 |
| M.I&S Palvelut Oy | Other services | 2025 |
| M.Tuhkalainen Oy | Professional & scientific | 2021 |
| M2 Management Oy | Wholesale & retail | 2011 |
| MF Realty Ky | Construction | 2008 |
| MHNS Invest Oy | Arts & recreation | 2026 |
| Mikkelin Keskusbaari OY | Hospitality | 2008 |
| MKK Toimistotarvike Oy | Wholesale & retail | 2006 |
| MKM Urakointi Oy | Agriculture & fishing | 2026 |
| MM Infra Oy | Construction | 1987 |
| MO Tervo Oy | Hospitality | 2017 |
| Motohalli OY | Administrative & support | 2008 |
| MPY Telecom Oy | Professional & scientific | 2023 |
| MR.Osaajat Oy | Wholesale & retail | 2022 |
| MSProfylaksia Oy | Health & social care | 2014 |
| MTA Järvinen Oy | Construction | 2022 |
| MV Property Consulting Oy | Real estate | 2007 |
| MV-Rent Oy | Construction | 2020 |
| MX Solutions Oy | Wholesale & retail | 2018 |
| MaSa Sijoitus Oy | Other services | 1986 |
| Maakunnan Kone Oy | Manufacturing | 2015 |
| Maalaus ja Pinnoitus Ahtiainen Oy | Construction | 2006 |
| Maalaus- ja Sisustuspalvelu R Konttinen Ky | | 1989 |
| Maalausliike Pöntinen Oy | Construction | 1980 |
| Maalausliike Valjakka Ky | Construction | 1982 |
| Maalipinta Meriläinen Oy | Construction | 2008 |
| Maankäyttöpalvelut Jarmo Vauhkonen Oy | Professional & scientific | 1990 |
| Maanmittauspalvelu Puttonen Oy | Professional & scientific | 2000 |
| Maanrakennus Hyyryläinen Oy | Construction | 2011 |
| Maansiirto- ja rakennusyhtymä Harri & Ari Pulkkinen | Construction | 1985 |
| Madkid World Oy | Wholesale & retail | 2022 |
| Maihniemen Meklari- ja Rh-palvelut Oy | Financial services | 2018 |
| Maija Klippa Oy | Other services | 2007 |
| Mainospihlaja Ky | Professional & scientific | 2006 |
| Mainostalo Mainospuu Oy | Professional & scientific | 1990 |
| Mainostoimisto Aamu Media Oy | Professional & scientific | 2008 |
| Mainostoimisto Groteski Oy | Professional & scientific | 2012 |
| Maksimatti Oy | Professional & scientific | 1994 |
| Makuuni Oy | Administrative & support | 2005 |
| Malliakopio Ky | Professional & scientific | 1984 |
| Mammutti 3000 Oy | Hospitality | 2010 |
| Manpas Oy | Water & waste | 2024 |
| Marja Turunen Oy | Hospitality | 1996 |
| Markkinointi Nordmech Oy | Wholesale & retail | 1996 |
| Markkinointi Raija-Liisa Oy | Wholesale & retail | 1986 |
| Markkinointitoimisto Groteski Oy | Professional & scientific | 2024 |
| Markku Paalanen Ky | Manufacturing | 1980 |
| Marski Data Oy | Wholesale & retail | 2012 |
| Marskin Katsastus Oy | Professional & scientific | 2019 |
| Marskin Kiinteistö Oy | Real estate | 2023 |
| Marskin Kioski-Kahvio Oy | Wholesale & retail | 2014 |
| Marttilan Lava Ky | Manufacturing | 1983 |
| Marttulit Oy | Administrative & support | 2023 |
| MasaTrades Oy | Financial services | 2026 |
| Matin Kiinteistö- ja Koulutuspalvelut Oy | Real estate | 2013 |
| Matkailu-Majoitus Oy | Administrative & support | 1976 |
| Matrel Oy | Manufacturing | 2012 |
| Matti Kunnas Oy | Financial services | 1994 |
| Mattohuolto Pyykkärit Oy | Other services | 2022 |
| Mattotyö Kiviluoto Oy | Construction | 2020 |
| Maunuks Oy | Wholesale & retail | 2023 |
| Mauri Keijonen Ky | Construction | 2006 |
| Mavacom Oy | Information & communication | 2007 |
| Mayt Oy | Professional & scientific | 1992 |
| Mealvation Oy | Information & communication | 2015 |
| Mecatroplan Mikkeli Oy | Professional & scientific | 2012 |
| MedicPlaza Oy | Health & social care | 2018 |
| Mediovi Oy | Health & social care | 2023 |
| Medscion Pharma Solutions Oy | Information & communication | 2024 |
| Mehevä Inkivääri Oy | Hospitality | 2022 |